The researchers began with a previously published single-cell RNA-sequencing atlas of adult chicken anterior pituitary tissue. In that dataset, GRP was detected primarily in gonadotrophs from female chickens, with additional expression in lactotrophs and folliculo-stellate cells. This distribution was consistent with an earlier report that GRP-immunoreactive cells in the chicken pituitary largely overlap with luteinizing hormone-positive cells. The researchers also consulted a domestic chicken multi-tissue expression database, which showed abundant GRP and GnRH receptor 2 messenger RNAs in the anterior pituitary of adult chickens. Because GnRH1 is a central regulator of reproductive hormone synthesis and secretion, the localization of GRP in gonadotrophs made it a plausible target for GnRH control.

To test this possibility, investigators dispersed and cultured anterior pituitary cells collected from one-week-old chicks. The cells were initially maintained in serum-containing medium and then transferred to serum-free conditions before hormone treatments. Quantitative real-time polymerase chain reaction was used to measure GRP messenger RNA, with β-actin and GAPDH serving as reference genes. GnRH1 at 100 nanomolar increased GRP expression in the cultured cells, with the strongest response after six hours. A concentration series showed that 0.1–100 nanomolar GnRH1 produced a dose-dependent increase, with a statistically significant response at the lowest tested concentration. The experiment therefore established a direct response in cultured pituitary cells rather than demonstrating regulation in an intact bird.

Drug experiments were then used to probe the intracellular pathways associated with the GnRH1 response. Forskolin, an activator of adenylyl cyclase, mimicked the increase in GRP expression and did so in a dose-dependent manner. Blocking adenylyl cyclase with MDL-12,330A completely abolished the effect of 10 nanomolar GnRH1 after six hours and also reduced basal GRP expression. The protein kinase A inhibitor H89 markedly suppressed the GnRH1 response and likewise lowered basal expression. These results support participation of the adenylyl cyclase–cyclic AMP–protein kinase A pathway, although the study did not directly measure cyclic AMP or protein kinase A activation.

A second set of inhibitors indicated that another signaling route also contributed. Phorbol 12-myristate 13-acetate, a protein kinase C activator, reproduced the dose-dependent stimulation produced by GnRH1. Inhibition of phospholipase C with U73122, inhibition of protein kinase C with calphostin C, or inhibition of mitogen-activated protein kinase kinase with PD98059 significantly reduced GnRH1-induced GRP expression. The authors therefore proposed involvement of the phospholipase C–protein kinase C–mitogen-activated protein kinase kinase–extracellular signal-regulated kinase pathway. The pharmacological design supports pathway participation but cannot establish every molecular interaction directly, and the experiments did not determine which GnRH receptor subtype mediated the response or whether GRP protein secretion changed alongside its messenger RNA.

The sex-steroid experiments produced distinct regulatory patterns in the same culture system. The androgen 5α-dihydrotestosterone reduced GRP messenger RNA after 48 hours, with stronger inhibition as concentration rose from 1 to 100 nanomolar. Progesterone also reduced GRP expression in both time- and dose-dependent tests: 100 nanomolar progesterone had an effect over a 12–48-hour interval, and concentrations from 1 to 1,000 nanomolar produced progressively lower expression after 48 hours. By contrast, 17β-estradiol increased GRP expression. Its largest response occurred after 12 hours, and a concentration series showed stimulation at 0.1–100 nanomolar. Diethylstilbestrol, an estradiol analogue, also increased GRP expression dose dependently.

Blocking the estradiol response with 4-hydroxytamoxifen, an estrogen-receptor antagonist, indicated that the increase depended on receptor-mediated signaling. The investigators then cloned 1,914 base pairs of the chicken GRP gene’s 5′ flanking region and analyzed it with promoter-prediction tools. The sequence had a reported GC content of 57.26 percent. Two predicted estrogen-receptor-binding sites were located at positions −914 and −411 base pairs relative to the transcription start site. A full-length promoter fragment produced approximately 16-fold more luciferase activity than an empty control vector in chicken DF-1 cells and approximately 12-fold more in human HEK293 cells. Removing the region upstream of −914 base pairs did not significantly reduce basal activity, placing most of the measured promoter activity in the proximal 915-base-pair region.

Estradiol also increased activity of the GRP promoter in DF-1 cells, while the authors then used site-directed deletions to test the two predicted receptor sites. Estradiol significantly stimulated the intact construct and a construct lacking the first site, but no significant response was detected when the second site was deleted or when both sites were removed. Responses from the second-site and double-deletion constructs were also significantly lower than that of the intact promoter. These results provide a functional basis for estrogen regulation of the GRP gene, though they do not prove direct receptor occupancy. The authors noted that receptor-specific loss-of-function or knockdown experiments would be needed to distinguish direct effects from other sequence elements, spacing effects and transcription-factor interactions.

The steroid results also revealed that estradiol did not regulate all gonadotroph signals in the same way. In cultured pituitary cells, 17β-estradiol reduced follicle-stimulating hormone beta messenger RNA while increasing GRP messenger RNA. The divergence is notable because both products are associated with gonadotrophs and ovarian follicle development. Earlier work had shown that the GRP receptor is abundant in granulosa cells of small chicken ovarian follicles and that GRP can promote granulosa-cell proliferation and follicle survival. The authors proposed that increased pituitary GRP might therefore support the survival of small follicles that could later enter the preovulatory hierarchy, whereas reduced FSH beta expression reflects a different arm of estrogen feedback.

That reproductive interpretation remains a hypothesis rather than a demonstrated outcome. The researchers suggested a possible positive-feedback model in which growing follicles produce more estradiol, higher estradiol stimulates more pituitary GRP expression, and GRP then helps preserve additional small follicles. This model was linked to an earlier association between circulating estradiol-to-progesterone ratios and egg production across eight chicken genetic stocks, but the present experiments neither manipulated egg laying nor measured follicular survival after altering GRP. The study also did not measure GRP secretion, establish whether secretion varies among breeds, or test gene knockout. These limitations are important because the experiments were performed in cultured cells, often from young chicks, whereas the proposed reproductive role involves adult ovarian function and whole-animal physiology.

Taken together, the results identify cGRP as a molecular target of GnRH1 and sex-steroid feedback in chicken pituitary cells. GnRH1 increased GRP expression through pathways that probably include cyclic AMP–protein kinase A and phospholipase C–protein kinase C–mitogen-activated protein kinase kinase–extracellular signal-regulated kinase signaling. Androgen and progesterone suppressed the transcript, while estradiol increased it through a response involving two potential estrogen-receptor-binding sites in the proximal promoter. The work provides a detailed regulatory map for a proposed chicken pituitary hormone and connects it mechanistically to the previously reported survival-promoting effect of GRP in small ovarian follicles. Whether that regulatory circuit actually changes follicle selection, egg production or reproductive performance will require studies in living chickens, including direct tests of GRP secretion and loss of function.

Subject of Research: Hormonal regulation of gastrin-releasing peptide expression in chicken pituitary cells and its possible role in ovarian follicle survival

Article Title: Regulation of gastrin-releasing peptide gene expression in chickens

Article References: Tang, K., Tian, X., Yuan, X., Li, Y., Zhang, J., Wang, Y., & Li, J. (2026). Regulation of gastrin-releasing peptide gene expression in chickens. Frontiers in Physiology, 17, 1940305. https://doi.org/10.3389/fphys.2026.1940305

Image Credits: AI Generated

DOI: 10.3389/fphys.2026.1940305

Keywords: chicken, gastrin-releasing peptide, pituitary gland, GnRH1, estrogen, sex steroids, gene regulation, ovarian follicles, egg production, Regulation, gastrin-releasing, peptide

Researchers compared women receiving systemic estrogen-only therapy with women receiving systemic estrogen-plus-progestogen therapy after one-to-one propensity score matching. Outcomes included composite autoimmune disease and 20 individual autoimmune diseases recorded 180 days or more after hormone therapy began. For composite autoimmune disease, the estimated event proportions were 4.9% in the estrogen-only group and 4.5% in the estrogen-plus-progestogen group.

The corresponding hazard ratio was 1.08, with a 95% confidence interval of 1.02 to 1.14. These results indicate a small association between estrogen-only treatment and the measured rate of newly recorded composite autoimmune disease, but they do not establish that either formulation causes autoimmune disease. The disease-specific analysis found significantly higher hazards among women receiving estrogen-only therapy for systemic lupus erythematosus, rheumatoid arthritis, psoriasis, psoriatic arthritis, multiple sclerosis and lichen sclerosus.

No significant differences were observed for the other autoimmune diseases included in the study. The news release did not provide separate event counts, absolute risk differences or effect estimates for each individual disease, so the size of those associations cannot be evaluated from the reported results. The comparison was also limited to systemic hormone therapy formulations; the evidence supplied does not address other routes, doses, durations or hormone products.

Progestogen is included in hormone therapy to protect the uterus, and the study was designed to determine whether adding it changes the autoimmune-disease association associated with menopausal hormone therapy. The results suggest that the presence of progestogen may limit the increased hazard associated with estrogen alone. For composite autoimmune disease, the reported event proportions differed by 0.4 percentage points.

The release did not state follow-up duration or present absolute risk differences for the six conditions with higher hazards, limiting interpretation of their clinical significance. The researchers said prospective studies are needed to clarify the immunologic effects of different menopausal hormone therapy formulations. “Our findings suggest that the autoimmune disease risk associated with menopausal hormone therapy may differ by hormone formulation,” said Dr.

Xuezhi Daniel Jiang, lead author and professor of obstetrics and gynecology at Drexel University College of Medicine. She emphasized that estrogen-only therapy was associated with only a modestly higher risk than estrogen-plus-progestogen therapy and that the absolute differences were small. Dr.

Stephanie Faubion, medical director for The Menopause Society, said studies like this are important for informing future prospective investigations of the association between hormone therapy and autoimmune diseases, which are more common in women than in men. The study, titled “Incident autoimmune disease risk in systemic estrogen versus estrogen-progestogen menopausal hormone therapy,” was scheduled for presentation at The Menopause Society’s 2026 Annual Meeting in San Diego on October 20–24, 2026. The supplied news release reported no conflicts of interest.

Because the evidence did not include the full paper, details such as matching variables, eligibility criteria, follow-up duration, sensitivity analyses and complete disease-specific results were unavailable. The supported conclusion is therefore limited: among the matched cohort, systemic estrogen-only therapy was associated with slightly higher measured hazards for composite and selected autoimmune diseases than systemic estrogen-plus-progestogen therapy, but the absolute differences were small, causality was not demonstrated and prospective investigation is required.

Subject of Research: Comparison of incident autoimmune disease hazards between systemic estrogen-only and estrogen-plus-progestogen menopausal hormone therapy

Article Title: Autoimmune disease risk may differ by menopausal hormone therapy formulation

Article References: Autoimmune disease risk may differ by menopausal hormone therapy formulation. Original publication (Bibliographic details unavailable.)

Image Credits: AI Generated

DOI: Not provided

Keywords: menopause, hormone therapy, autoimmune disease, estrogen, progestogen, observational study, TriNetX, systemic lupus erythematosus, rheumatoid arthritis, psoriasis, Autoimmune, disease

Investigators used dual-energy X-ray absorptiometry, or DEXA, to assess bone mineral density at the lumbar spine, femoral neck and hip. Measurements were taken at baseline, after participants had received estrogen therapy alone for at least one year, and after they had received estrogen plus testosterone for at least one year. The mean duration of estrogen-only therapy was 3.5 years, while the mean duration of combined estrogen and testosterone therapy was 3.1 years.

Across the study, participants were followed for an average of 4.1 years. The analysis compared T-scores at the three skeletal locations across these sequential treatment periods. Estrogen therapy alone did not produce a statistically significant increase in T-scores at the lumbar spine, femoral neck or hip.

In contrast, estrogen plus testosterone was associated with a significant increase in the lumbar spine T-score. The femoral neck and hip T-scores remained stable across both treatment periods, making the spine the only measured site where the researchers reported a significant increase after combined therapy. The release did not provide the numerical T-score changes, DEXA values, confidence intervals or other effect estimates, so the magnitude and precision of the observed association cannot be determined from the information supplied.

Based on the site-specific pattern, Davis and colleagues suggested that testosterone may have a synergistic effect with estrogen on trabecular bone, with the clearest measured association occurring at the spine. This was the investigators’ interpretation of the results rather than a separately demonstrated biological mechanism. The observational design and the sequence of estrogen-only and combined treatment mean that the findings establish an observed association, not a causal effect of adding testosterone.

Information about participant characteristics, adverse events and adherence was not included in the release. Bone density can decrease substantially during and after menopause as estrogen levels fall, and the release notes that women may lose 10% to 20% of their bone density in the first five to seven years after menopause. This rapid thinning raises the risk of osteopenia, described as low bone mass, and osteoporosis, characterized by weak, brittle bones that are prone to fracture.

Estrogen therapy has historically been prescribed to lower the risk of spine and hip fractures, while weight-bearing and resistance exercise, adequate calcium and vitamin D intake and hormone therapy are described as proven methods for protecting bone health. The present findings do not report a fracture outcome, and Davis said further research is needed to determine how testosterone could be used safely and effectively in individualized menopausal care. Stephanie Faubion, medical director of The Menopause Society, similarly emphasized the need for more studies exploring options that may help protect women’s bones during and after menopause.

Subject of Research: Bone mineral density during sequential estrogen and combined estrogen-testosterone therapy in postmenopausal women

Article Title: Combined estrogen and testosterone therapy increases lumbar spine bone mineral density

Article References: Combined estrogen and testosterone therapy increases lumbar spine bone mineral density. Original publication (Bibliographic details unavailable.)

Image Credits: AI Generated

DOI: Not provided

Keywords: postmenopausal women, bone mineral density, estrogen therapy, testosterone therapy, lumbar spine, osteoporosis, menopause, DEXA, Combined, estrogen, testosterone, therapy

The study drew on 4,209 volunteers recruited between January 2022 and December 2023 through the First Affiliated Hospital of Guangzhou Medical University (Loudi Hospital), including 2,898 women and 1,311 men. All participants were healthy controls screened to exclude active immune disorders, malignancies, recent infections, and immunosuppressive therapy. Researchers measured ten immune parameters in peripheral blood using flow cytometry, covering total T cells, CD4+ and CD8+ T cell subsets, the CD4/CD8 ratio, B cells, natural killer cells, NKT cells, and expression of the checkpoint molecule PD-1 on several cell types.

Because raw immune measurements rarely follow a normal distribution, the team applied Box-Cox transformations and Tukey’s method to remove outliers before analysis, leaving between 4,123 and 4,204 reference individuals per parameter. Age-related trends were then examined with sex-stratified smooth curves and non-parametric tests, and a 1:1 propensity score matching procedure was used to build age-balanced male and female cohorts for direct comparison.

The headline finding is a sharp sexual dimorphism in B cell dynamics. In women, the proportion of CD19+ B cells rose with age, while in men it fell, producing opposite trajectories that the authors link tentatively to hormonal regulation and X-chromosome-encoded immune genes. After age matching, women had significantly higher B cell percentages than men, but a stratified analysis showed this gap was not significant before age 50 and only emerged after menopause, pointing to the postmenopausal window as the critical period.

T cell subsets told an equally striking story. In women, CD4+ helper T cells and the CD4/CD8 ratio climbed to a peak in the 55-to-59-year age group, while CD8+ cytotoxic T cells declined steadily across the lifespan. The authors describe this as a “scissor-like” pattern that closely parallels the abrupt drop in estrogen levels around menopause. Because hormone levels were not directly measured, they caution that this mechanistic interpretation remains speculative, but the timing of the immune shift aligns closely with the typical age of menopause as defined by the STRAW+10 staging framework.

PD-1, an immune checkpoint molecule best known as the target of modern cancer immunotherapies, showed a complex, cell-type-specific pattern. Women had lower PD-1 expression on CD4+ T cells and NK cells but higher PD-1 on CD8+ T cells, and the proportion of CD8+ PD-1+ cells showed a transient peak in the 60-to-64-year group. The authors suggest this may mark a window of heightened functional dysregulation in cytotoxic immunity, with potential relevance for how immune checkpoint status should be interpreted across demographic groups.

Innate immunity shifted as well. Natural killer cell percentages increased with age in both sexes, but the rise was markedly steeper in men, and the fraction of NK cells expressing PD-1 declined significantly with age in women. NKT cells, by contrast, showed no significant age-related trend. After age matching, women had higher NK cell and NKT cell proportions than men, alongside their higher CD4/CD8 ratios, reinforcing the picture of two distinct immune aging trajectories.

The findings carry practical implications. Because women generally mount stronger vaccine responses but suffer more autoimmune disease, and because PD-1 expression shapes anti-tumor immunity and postoperative infection risk, the authors argue that both sex and reproductive stage should be factored into studies of immune aging and into interventions such as vaccination strategies for middle-aged women. The observed B cell persistence in older women may represent a distinctive adaptive feature of female immunosenescence, though its consequences for humoral immunity remain to be tested.

The study has clear limitations. It is cross-sectional, so it captures age-related differences between individuals rather than tracking immune changes within the same person over time. Without menstrual records or hormone measurements, the researchers could not formally stage participants under STRAW+10 and instead used age groups as an approximation, meaning the 50-to-54-year group inevitably mixes perimenopausal and early postmenopausal women. The authors call for longitudinal studies that pair hormone monitoring with systematic reproductive staging to confirm whether the menopausal transition itself drives the immune shifts observed here.

Even with those caveats, the scale of the cohort and the consistency of the sex differences make a strong case that immunosenescence is not a single process but two, diverging sharply at midlife. For a field in which clinical trial populations and reference ranges have historically skewed male, the message is that middle-aged women may need their own immunological yardsticks, and that menopause deserves a place alongside chronological age as a variable in immune research.

Subject of Research: Sex differences in lymphocyte subset changes during the menopausal transition and immunosenescence

Article Title: Dynamic Shifts in Lymphocyte Subsets During the Menopausal Transition and Sexual Dimorphism in Immunosenescence

Article References: Xuan, C., He, L., Bohan, Z., Junming, X., Qingchao, L., & Junting, H. (2026). Dynamic Shifts in Lymphocyte Subsets During the Menopausal Transition and Sexual Dimorphism in Immunosenescence. Immunity, Inflammation and Disease, 14(10), Article e70558. https://doi.org/10.1002/iid3.70558

Image Credits: AI Generated

DOI: 10.1002/iid3.70558

Keywords: immunosenescence, menopause, lymphocyte subsets, PD-1, T cells, B cells, natural killer cells, sexual dimorphism, flow cytometry, estrogen, immune aging, propensity score matching

The research, published in Frontiers in Allergy, examined perimenopausal women aged 45 to 60 years and compared them against patients with chronic non-fungal sinusitis, a control group that shares many symptoms but lacks the fungal mass at the heart of the disease. The team focused on two metabolic markers that have become central to modern cardiovascular and endocrine research: high-density lipoprotein cholesterol, the so-called good cholesterol, and a composite index known as TyG-BMI, which combines the triglyceride-glucose index with body mass index to capture insulin resistance and overall metabolic burden. Both markers are inexpensive to measure, which makes any association with a fungal sinus disease immediately interesting from a screening standpoint.

Fungal ball sinusitis, sometimes called fungus ball or aspergilloma of the paranasal sinuses, belongs to the non-invasive category of fungal sinus disease. Unlike invasive fungal infections that threaten immunocompromised patients, a fungal ball grows slowly within a blocked sinus cavity, forming a compact tangle of hyphae that surgeons must physically remove. The condition typically affects one sinus, most often the maxillary sinus, and produces chronic nasal obstruction, foul discharge, facial pressure and, in some cases, the sensation of a foreign body deep in the cheek. Because its symptoms mimic ordinary chronic rhinosinusitis, diagnosis frequently arrives only when computed tomography reveals characteristic calcifications or when the removed tissue is examined under a microscope.

The study design was straightforward but carefully targeted. The researchers enrolled fungal ball sinusitis patients treated at their single center between 2015 and 2025, then narrowed the analysis to perimenopausal women aged 45 to 60, using patients with chronic non-fungal sinusitis as the comparison group. Biochemical indicators were compared between the two groups, participants were sorted into quartiles based on their TyG-BMI values, and logistic regression models were used to identify which factors independently predicted fungal ball disease. Receiver operating characteristic curves, a standard tool for judging diagnostic performance, were then applied to test whether the metabolic markers could actually predict the condition.

The demographic findings alone tell a compelling story. Across the decade of cases, fungal ball sinusitis showed a steadily increasing trend, and the patient population skewed heavily toward middle-aged and elderly individuals. Women made up 63.96 percent of cases compared with 36.04 percent of men, and the peak age of female illness clustered tightly between 45 and 60 years, precisely the window of perimenopause. This concentration is exactly the kind of pattern that makes researchers suspect hormonal and metabolic mechanisms rather than simple exposure, since perimenopause is accompanied by falling estrogen levels, redistribution of body fat, rising insulin resistance and deteriorating lipid profiles.

When the researchers compared blood values between the two groups, the differences were clear. Women with fungal ball sinusitis had significantly lower HDL cholesterol levels and significantly higher TyG and TyG-BMI values than women with chronic non-fungal sinusitis. The relationship held up in a dose-response pattern: as TyG-BMI quartiles rose, HDL cholesterol fell progressively, and the prevalence of fungal ball sinusitis climbed in step. In statistical terms, the trend was significant at P less than 0.05, meaning the probability that these gradients arose by chance is small.

The logistic regression analysis then isolated the two markers as independent risk factors, each holding its predictive power after accounting for the other. Higher HDL cholesterol was protective: each unit increase was associated with an odds ratio of 0.482, with a 95 percent confidence interval of 0.282 to 0.823 and a P value of 0.008, meaning women with better HDL levels had roughly half the odds of fungal ball disease. Higher TyG-BMI, by contrast, carried risk, with an odds ratio of 1.192 per quartile step, a 95 percent confidence interval of 1.008 to 1.409 and a P value of 0.04. In plain language, the more insulin-resistant and metabolically burdened a woman was, the more likely she was to harbor a fungal ball in her sinuses, and the healthier her cholesterol profile, the lower that likelihood became.

One finding deserves careful interpretation. When the researchers combined TyG-BMI and HDL cholesterol into a single predictive model and tested it with ROC analysis, the combined model showed only limited predictive value for fungal ball sinusitis. This means the markers are statistically associated with the disease and may illuminate its biology, but they cannot yet serve as a reliable diagnostic test in the clinic. Association is not prediction, and a screening tool built on these numbers would miss too many cases and flag too many healthy women to be useful on its own. The authors instead frame their results as a call for targeted metabolic monitoring and early intervention, positions that could plausibly lower fungal ball risk if the underlying mechanisms hold up in future work.

What might those mechanisms be? The study was observational and retrospective, so it cannot prove causation, but the biology offers several plausible threads. Insulin resistance, which TyG-BMI captures, is known to alter mucosal immunity, promote low-grade systemic inflammation and change the composition of airway secretions, all of which could make the sinus environment more hospitable to fungal colonization. HDL cholesterol, meanwhile, does far more than ferry lipids; it modulates inflammation and immune cell function, and low HDL is a recognized hallmark of metabolic syndrome. Falling estrogen during perimenopause worsens both insulin resistance and lipid profiles, which could explain why the disease concentrates in this demographic window. A clogged, inflamed, metabolically altered sinus cavity may simply be easier for ambient fungal spores to colonize and harder for the immune system to clear.

The clinical takeaway is that fungal ball sinusitis should no longer be viewed as a purely local problem of the nose. For perimenopausal women with stubborn unilateral sinus symptoms, especially those with known metabolic risk, the study suggests that clinicians may want to look at the whole metabolic picture rather than treating the sinus in isolation. The rising annual incidence recorded at this single center over ten years adds urgency, because a disease that grows quietly in midlife women is a disease that health systems will increasingly encounter. Larger multicenter prospective studies will be needed to confirm the association, test whether metabolic intervention actually reduces risk, and determine whether TyG-BMI and HDL cholesterol can eventually earn a place in clinical prediction models. For now, the message is that the sinuses and the metabolism are more connected than anyone suspected, and the blood panel drawn for a routine midlife checkup may one day help flag the women who need a closer look up their nasal passages.

Subject of Research: Metabolic risk factors for fungal ball sinusitis in perimenopausal women

Article Title: Metabolic risk factors for fungal ball sinusitis in perimenopausal women

Article References: Wang, S.-Y., Xu, W., Liu, Y.-X., Jiang, L., Xu, Y., Teng, F.-Y., Hu, X.-Y., & Li, H.-X. (2026). Metabolic risk factors for fungal ball sinusitis in perimenopausal women. Frontiers in Allergy, 7, 1900638. https://doi.org/10.3389/falgy.2026.1900638

Image Credits: AI Generated

DOI: 10.3389/falgy.2026.1900638

Keywords: fungal ball sinusitis, perimenopausal women, TyG-BMI, HDL cholesterol, insulin resistance, chronic rhinosinusitis, metabolic syndrome, Frontiers in Allergy, retrospective study, sinus disease, estrogen, logistic regression

The research team, led by Robin Kruger and senior author Ariella Shikanov, set out to answer a question that clinical studies have struggled to resolve: does testosterone worsen, mitigate, or simply modify the consequences of ovarian hormone loss? Human studies of exogenous testosterone administration show inconsistent effects on lipid profiles, insulin sensitivity, body weight, and blood pressure, and they are often constrained by retrospective designs, heterogeneous hormone regimens, and confounding variables such as participant age and baseline metabolic status. Crucially, none of these studies have examined potential differences in outcomes between patients with and without endogenous ovaries. A controlled animal model offered a way to isolate the direct physiological effects of testosterone and ovarian hormone loss on metabolism and the skeleton.

The experiment was elegantly simple in design. Eight-week-old adult female CD-1 mice underwent either sham surgery or ovariectomy, and at the same time were implanted subcutaneously with silastic capsules containing either 10 milligrams of testosterone powder or empty control capsules. This produced four experimental groups: intact mice with empty capsules, ovariectomized mice with empty capsules, intact mice with testosterone, and ovariectomized mice with testosterone, with seven to eight animals per group. After six weeks of treatment, the researchers measured fasting glucose, glucose tolerance, serum lipids, insulin, reproductive hormones, fat pad weights, adipocyte size, heart and liver phenotypes, and bone density and strength. Serum testosterone rose to the range typically observed in male mice in both testosterone-treated groups, confirming that the treatment produced a genuinely hyperandrogenic hormonal milieu.

The most dramatic result concerned glucose metabolism. Mice that lost their ovaries without testosterone replacement developed hyperglycemia and impaired glucose tolerance, consistent with previous studies of ovariectomy-induced metabolic dysfunction. Yet ovariectomized mice receiving testosterone retained entirely normal glucose function, indistinguishable from intact controls. Testosterone treatment was sufficient to prevent the ovariectomy-induced glucose metabolism defects, even though fasting insulin levels did not change proportionally. This suggests that testosterone supplementation alone can maintain glucose homeostasis in the absence of ovarian hormones, a finding with direct implications for how clinicians might think about metabolic risk after estradiol depletion.

Bone told an equally compelling story. Using nano-computed tomography of the femur and three-point bending tests of the radius, the team found that testosterone increased trabecular bone number, reduced trabecular spacing, and raised bone density measures regardless of whether the ovaries were present. Both testosterone-treated groups showed congruent trends toward greater maximum load and bending stiffness in mechanical testing. Interestingly, trabecular thickness was not increased despite the greater number of trabeculae, consistent with previous reports in mice and humans that testosterone induces formation of more but thinner trabeculae. Testosterone had minimal impact on cortical bone, supporting clinical evidence that cortical microstructure is not as strongly regulated by androgen signaling. Together, these data demonstrate that elevated testosterone is sufficient not only to prevent ovariectomy-associated bone loss but to raise trabecular bone density above baseline even without endogenous gonads.

But the story was not uniformly rosy. Testosterone could not prevent dyslipidemia in the absence of ovaries. Both ovariectomized groups, whether treated with testosterone or not, displayed elevated fasting total cholesterol and HDL cholesterol levels compared with intact mice. In mice, which carry most plasma cholesterol in HDL particles, elevated HDL more likely reflects overall hypercholesterolemia rather than a protective phenotype as it might in humans. Similarly, ovariectomy increased adipocyte size in both inguinal and perigonadal fat pads regardless of testosterone treatment, indicating adipocyte hypertrophy persisted despite the androgen excess. In contrast, testosterone-treated mice with intact ovaries showed decreased fat pad weight and smaller median adipocyte size, a pattern aligning with sexual dimorphism in body composition where males carry lower adiposity than females. The researchers concluded that lipid metabolism is more sensitive to estradiol levels than to testosterone levels, and that testosterone aromatized in non-ovarian tissues is not sufficient to maintain lipid homeostasis in females.

The heart added another layer of complexity. Testosterone treatment significantly increased heart weight in both ovary-intact and ovariectomized mice compared with untreated controls, supported by congruent trends toward increased heart longitudinal area and left ventricular cardiomyocyte size. Neither testosterone nor ovariectomy significantly impacted heart fibrosis, liver weight, collagen deposition, or hepatic lipid content over the six-week period. The researchers argue that these changes are more likely direct androgenic effects rather than consequences of reduced estradiol, because ovariectomized mice without testosterone did not exhibit the same phenotypes. This premise is consistent with prior studies showing that males generally have greater heart mass and higher triglyceride levels than females, and that testosterone can induce cardiomyocyte hypertrophy in vitro through androgen receptor signaling.

One of the most intriguing findings involved the uterus. Testosterone-treated mice with intact ovaries showed increased uterine weight and cross-sectional area, a uterotrophic effect suggesting significant aromatization of testosterone into estradiol and estrogenic signaling, despite the cessation of estrous cycling. Meanwhile, ovariectomized mice without testosterone showed the expected uterine regression. Remarkably, the uteri of testosterone-treated ovariectomized mice were indistinguishable from intact controls, avoiding both testosterone-induced hypertrophy and ovariectomy-induced atrophy. If the uterotrophic effect comes from aromatization into estradiol, this would indicate that peripheral tissues alone can generate bioactive levels of estradiol to sustain uterine morphology. Alternatively, the effect could reflect direct androgen receptor signaling in uterine tissue. Either mechanism suggests that testosterone treatment and ovariectomy do not produce identical hormonal environments, despite similar repression of estrous cycling, and such differences in estrogenic activity may explain how testosterone-treated intact mice differ from ovariectomized groups in metabolic outcomes such as adiposity and cholesterol.

The study faces limitations, particularly in determining the mechanisms governing the observed metabolic changes. A primary shortcoming is the inability to distinguish which effects of testosterone administration result from androgen signaling and which may be due to aromatization of testosterone into estradiol. Many peripheral tissues express aromatase, and this mechanism is undoubtedly at play even in ovariectomized animals. Previous studies have shown that aromatization is critical for the beneficial effects of androgen administration on rodent metabolism and skeletal health. Future studies may employ aromatase inhibition or androgen receptor knockout models to separate these two pathways, along with insulin tolerance testing, estradiol measurements, and quantification of metabolic gene expression. It is also worth noting that several metabolic endpoints, including fasting insulin, metabolic tissue fibrosis, and hepatic lipid accumulation, were unaffected by either testosterone or ovary status, likely reflecting the resistance of CD-1 mice to hepatic steatosis on a standard diet and highlighting the importance of genetic background and diet in determining susceptibility to reproductive hormone-associated metabolic disease.

Clinically, these distinctions matter enormously. For women with conditions characterized by high testosterone levels, including polyendocrine metabolic ovarian syndrome, congenital adrenal hyperplasia, environmental exposure, or androgen-producing tumors, several of which are common comorbidities with metabolic syndrome and obesity that worsen in peri-menopause, this study may inform which metabolic disease factors are likely to increase in risk after estradiol depletion and which may be compensated by high testosterone. The findings are also directly relevant to transmasculine patients receiving testosterone gender-affirming hormone therapy, especially those considering gender-affirming oophorectomy. The results suggest that testosterone therapy is sufficient to maintain normal glucose metabolism and bone density after oophorectomy, but that gonad retention may be protective with respect to lipid and adipose tissue regulation. Further research investigating the mechanisms of interaction between endogenous and exogenous hormones, effects in individuals with existing disease states such as obesity, diabetes, and cardiovascular disease, and potential mitigation strategies for metabolic risk factors will be crucial to support the health of hyperandrogenic patients.

Subject of Research: Endocrinology

Article Title: Testosterone treatment prevents most gonadectomy-induced metabolic and skeletal deficiencies in female mice

Article References: Kruger, R. E., Yohannes, H., Cho, E., Eisner, L., Pfau, D. R., Chan-Sui, R. K., Migotsky, N., Monteiro da Rocha, A., Killian, M. L., Moravek, M. B., Padmanabhan, V., & Shikanov, A. (2026). Testosterone treatment prevents most gonadectomy-induced metabolic and skeletal deficiencies in female mice. Frontiers in Endocrinology, 17, Article 1940100. https://doi.org/10.3389/fendo.2026.1940100

Image Credits: AI Generated

DOI: 10.3389/fendo.2026.1940100

Keywords: testosterone, ovariectomy, female mice, glucose metabolism, bone density, trabecular bone, dyslipidemia, adipocyte hypertrophy, estrogen, aromatization, hyperandrogenism, gender-affirming hormone therapy

The research, published in Physiological Reports, examined 49 healthy females aged 18 to 45 years, dividing them into three groups: those with natural menstrual cycles, those taking second-generation combined oral contraceptive pills, and those on third-generation formulations. The findings were striking. Fasting glucose concentrations were approximately 10 percent higher in second-generation pill users and roughly 12.5 percent higher in third-generation users compared to naturally cycling women. Even more dramatic, fasting triglycerides were elevated by 56 to 70 percent in pill users relative to their naturally cycling counterparts. These are not trivial differences for a population of young, healthy, normal-weight women.

What makes this study particularly valuable is the rigor with which the researchers controlled for variables that have plagued previous investigations. Earlier studies on oral contraceptives and metabolism have produced wildly inconsistent results—some reporting benefits, others harm, and still others no effect at all. The McMaster team identified several reasons for this confusion. Many prior studies failed to account for the phase of the pill cycle or menstrual cycle at which blood samples were drawn. Others compared short-term users to long-term users without accounting for the body’s adaptation over time. And critically, several lacked a proper control group of naturally cycling individuals, making it impossible to disentangle the effects of the pill from natural hormonal variation.

To address these methodological gaps, the researchers implemented what they describe as rigorous temporal controls. Participants attended two laboratory visits timed to coincide with their low-hormone and high-hormone phases. For naturally cycling women, this meant the early follicular phase (days 3 to 7) and the mid-luteal phase (approximately 7 days after ovulation, confirmed with at-home ovulation kits). For pill users, visits were scheduled during the placebo week and during the third week of active pill use—the highest hormone week for those on triphasic formulations. Blood samples were collected in a fasted state at consistent times of day, and all participants underwent dual-energy X-ray absorptiometry (DXA) scans to assess body composition with precision.

The results extended beyond glucose and triglycerides. The researchers also found that appendicular lean mass index—a measure of skeletal muscle mass in the arms and legs normalized to height—was approximately 10 percent lower in both pill-user groups compared to naturally cycling women. However, when lean mass was expressed as a percentage of total body mass rather than height, this difference disappeared, suggesting that the naturally cycling group may simply have had larger and leaner lower bodies rather than a fundamentally different muscle distribution. Leg lean mass also trended toward being lower in pill users, though this did not reach statistical significance.

One of the most intriguing findings emerged from an exploratory sub-analysis. When all participants were pooled into a single group, the researchers observed a moderate negative correlation between appendicular lean mass index and fasting glucose concentrations—but only during the high-hormone phase. This suggests that skeletal muscle mass may play a more active role in glucose regulation during certain hormonal contexts than previously appreciated. Skeletal muscle is responsible for as much as 75 percent of glucose uptake from the bloodstream following a carbohydrate-containing meal, making it a critical player in metabolic health. Previous research has shown that lower muscle mass predicts impaired fasting glucose in elderly women, and the current findings hint that this relationship may extend to younger populations under specific hormonal conditions.

The mechanisms behind these metabolic differences likely involve the synthetic estrogen ethinyl estradiol, which is contained in both second- and third-generation oral contraceptives. Endogenous 17β estradiol—the naturally produced form of estrogen—plays a beneficial role in energy metabolism. It facilitates insulin secretion, stimulates glucose uptake from the bloodstream, reduces hepatic glucose release, promotes the shift from lipid storage to lipid oxidation, and lowers circulating triglyceride concentrations. Crucially, chronic exposure to ethinyl estradiol dramatically suppresses the body’s own estrogen production. The researchers previously confirmed that circulating 17β estradiol concentrations were significantly lower in both pill-user groups compared to naturally cycling women during the high-hormone phase. It is therefore plausible that pill users simply had less natural estrogen available to perform these metabolic protective functions.

The divergence between pill generations adds another layer of complexity. Third-generation users had approximately 40 percent higher HDL cholesterol concentrations compared to second-generation users, and there was a trend toward a lower total cholesterol to HDL ratio in the third-generation group. This difference likely relates to the type of progestin used in each formulation. Second-generation pills contain androgenic progestins that may antagonize the lipid effects of ethinyl estradiol, while the less androgenic progestins in third-generation pills may instead enhance them. This finding underscores the importance of distinguishing not just between pill users and non-users, but between different generations and formulations of the pill itself.

Importantly, the researchers caution that the magnitude of these differences, while statistically significant, remains modest in absolute terms. Average fasting glucose in all three groups remained well below the clinical threshold for concern, and only one participant across the entire study met the criteria for metabolic syndrome. For young, healthy, normal-weight women, the pill is unlikely to meaningfully increase the risk of developing metabolic disease. However, the researchers note that these subtle shifts could become clinically relevant for individuals with preexisting risk factors. A woman whose fasting glucose sits at 5.1 millimoles per liter before starting the pill, for example, could cross the threshold into the elevated range with the kind of increase observed in this study.

As metabolic syndrome rates continue to rise worldwide—particularly among women aged 18 to 45, the demographic most likely to use oral contraceptives—these findings carry significant public health implications. They also suggest that researchers may need to reconsider how they design studies involving female participants. Rather than excluding pill users to control for hormonal variability, the authors propose that expanding eligibility criteria to include both naturally cycling women and pill users could actually increase female participation in physiological research while improving the relevance and generalizability of the results. Future work, they note, should also examine how newer long-acting hormonal contraceptives, such as hormonal intrauterine devices, influence metabolism and body composition, as their popularity has surged over the past decade.

Subject of Research: The effects of combined oral contraceptive pills on fasting glucose, lipid metabolism, and body composition in young healthy females

Article Title: Elevated fasting glucose and triglycerides in combined oral contraceptive users compared to naturally cycling females

Article References: Karaguesian, C., Williams, J. S., MacDonald, M. J., & Bell, K. E. (2026). Elevated fasting glucose and triglycerides in combined oral contraceptive users compared to naturally cycling females. Physiological Reports, 14(19), Article e71135. https://doi.org/10.14814/phy2.71135

Image Credits: AI Generated

DOI: 10.14814/phy2.71135

Keywords: oral contraceptives, fasting glucose, triglycerides, metabolic syndrome, estrogen, body composition, HDL cholesterol, insulin resistance, menstrual cycle, women's health, DXA, skeletal muscle

The review, led by Emily Gallmetzer and Kejal Kantarci, followed PRISMA guidelines and screened 461 records from PubMed, ultimately including 18 peer-reviewed studies assessed with the Newcastle-Ottawa Scale. Fourteen were rated good quality, two fair, and two poor. The imaging modalities spanned the full modern neuroimaging toolkit: 16 studies used in vivo structural magnetic resonance imaging, four used diffusion tensor imaging, two used functional MRI, and three used positron emission tomography. Study designs ranged from massive population cohorts such as the UK Biobank, with more than 13,000 imaged participants, to small case-control studies of women recruited from familial cancer clinics.

Definitions matter enormously in this literature, and the review highlights how inconsistent they have been. Premature menopause is defined as onset before age 40, and early menopause as onset between ages 40 and 44. Both can arise spontaneously or be induced by chemotherapy, pelvic radiation, or premenopausal bilateral oophorectomy, the surgical removal of both ovaries before natural menopause. By contrast, hysterectomy with ovarian conservation stops menstruation but preserves endocrine function and is not a cause of ovarian hormone loss. The hallmark consequence of spontaneous menopause is the gradual decline of estradiol, the predominant and most biologically active ovarian estrogen during reproductive life, whereas oophorectomy causes abrupt and complete loss of estradiol and all other ovarian hormones.

Estrogen is far more than a reproductive hormone. In the brain it has important antioxidative effects, contributes to the suppression of immune activation led by astrocytes and microglia, and supports cerebral energy metabolism by upregulating glucose transporters. Early estrogen loss has been associated in experimental studies with increased oxidative stress, accelerated neuroinflammatory processes, and dysregulated iron homeostasis within the central nervous system. Loss of estrogenic support may increase vulnerability to neuronal injury, gliosis, and accumulation of pathological proteins. Because ovarian hormones act on multiple organ systems, their early loss has systemic consequences that extend well beyond reproductive health, and this accelerated somatic aging may itself exacerbate brain aging.

Across the structural MRI studies, the review found regionally specific rather than global patterns of brain differences. Women with premature or early menopause showed lower gray-matter volume or cortical thickness in medial temporal, frontal, and basal forebrain regions. In population-based cohorts, women who underwent oophorectomy before age 50 showed smaller amygdala volume and thinner parahippocampal-entorhinal cortex compared with age-matched controls. A more recent Mayo Clinic study found that oophorectomy before age 46 was associated with thinner entorhinal cortex independent of age at imaging, whereas lower temporal-lobe cortical thickness emerged only at older ages. In women with idiopathic premature ovarian insufficiency, voxel-based analysis revealed regional reductions in the bilateral olfactory cortex and right parahippocampal gyrus, together with reduced cortical thickness in parietal and insular regions and smaller hippocampal subfield and thalamic volumes. Notably, no significant global gray-matter difference was observed in the full sample, and younger participants showed exploratory global differences that were uncorrected for multiple comparisons.

Diffusion tensor imaging added a complementary microstructural picture. This technique quantifies axonal architecture through metrics such as fractional anisotropy, which measures the directionality of water diffusion, and mean diffusivity, which serves as an inverse index of membrane density and tissue integrity. Reduced fractional anisotropy, often accompanied by increased mean diffusivity, indicates loss of axonal integrity and myelination. Women who underwent oophorectomy before age 40 showed lower fractional anisotropy and higher mean diffusivity in the anterior corona radiata, the genu of the corpus callosum, and the inferior fronto-occipital fasciculus. Strikingly, women whose oophorectomy occurred between ages 40 and 44 showed no such differences, a pattern consistent with a threshold or dose-response effect of earlier hormone deprivation. In spontaneous premature menopause, altered structural connectivity involved the olfactory cortex, amygdala, hippocampus, and thalamus, while global network topology remained relatively preserved.

Functional MRI, though available in only two studies from the same Canadian research group, provided convergent functional correlates. Women who underwent bilateral salpingo-oophorectomy without hormone therapy showed lower right posterior lateral hippocampal activation during novel face-name encoding compared with those who received hormone therapy. A later study from the same group found lower posterior hippocampal activation in both treated and untreated groups compared with age-matched controls, though it did not fully replicate the earlier group-specific pattern, and anterior hippocampal activation and raw task accuracy did not differ across groups. The convergence with structural findings is only partial, and independent replication in separate cohorts is needed before firm conclusions can be drawn.

The PET evidence, though limited to three studies, offers the most provocative molecular findings. In cognitively unimpaired women with elevated amyloid-beta, earlier age at menopause was associated with higher regional tau burden, with effects clustering in medial temporal, lateral temporal, parietal, and occipito-temporal regions, a distribution consistent with Braak staging of early-to-intermediate Alzheimer’s tau pathology. In the Mayo Clinic cohort, women who underwent oophorectomy before age 46 showed higher amyloid-beta load when imaged at older ages, and tau was elevated only at higher amyloid-beta levels. Women whose oophorectomy occurred between ages 46 and 49 showed no comparable biomarker differences. These findings suggest that a woman’s age at the time of menopause, rather than menopause type alone, may be the most sensitive determinant of later molecular vulnerability.

Mechanistically, the review proposes that early loss of ovarian hormones may weaken the brain’s compensatory reserves and converge on interconnected deleterious molecular pathways. Reduced estrogen levels may diminish neurotrophic support, leading to loss of synaptic density within the medial temporal lobe and reduced neuronal resilience to age-related stressors. Estrogen normally supports cerebral energy metabolism, and its loss may contribute to mitochondrial dysfunction and impaired cellular bioenergetics, resulting in a hypometabolic state where the brain metabolizes its own myelin-derived lipids for energy. This metabolic shift may increase production of reactive oxygen species, including superoxide and hydrogen peroxide, which can damage neuronal membranes and further destabilize mitochondrial function. Estrogen also regulates enzymes involved in amyloid-beta degradation, such as the insulin-degrading enzyme, supports autophagic flux, and helps maintain microglia in a homeostatic state, so its depletion may shift the brain toward chronic neuroinflammation and failed protein clearance.

The authors are careful to emphasize that the evidence remains heterogeneous and largely cross-sectional, limiting causal inference about the temporal sequence between ovarian hormone loss and neurobiological change. Sixteen of the 18 included studies used age cutoffs that reached into the usual-age menopause range of 45 to 54 years, meaning many reported associations cannot be tied specifically to premature or early menopause. Large volunteer cohorts such as the UK Biobank tend to recruit healthier participants than the general population, and almost all studies imaged women only once. The review’s conclusions are therefore best seen as a rationale for prevention-oriented research rather than established clinical guidance. Still, the convergent pattern across imaging modalities, spanning gray-matter atrophy, white-matter microstructural deficits, reduced hippocampal activation, and preliminary evidence of altered amyloid and tau burden, suggests that women’s reproductive history deserves consideration as an integral part of dementia risk profiles. Large-scale longitudinal studies tracking the same women with serial neuroimaging over years, and evaluating interactions with genetic predisposition such as the apolipoprotein E epsilon 4 genotype, are now needed to determine when brain alterations begin in relation to the drop in estrogen levels and whether specific critical windows exist during which hormonal interventions could decelerate degeneration in networks vulnerable to Alzheimer’s disease.

Subject of Research: Neuroscience

Article Title: Premature and early menopause and neuroimaging biomarkers of neurodegenerative diseases: a systematic review

Article References: Gallmetzer, E., Mak, E., Kara, F., Zeydan, B., Kapoor, E., Shufelt, C. L., Rocca, W. A., & Kantarci, K. (2026). Premature and early menopause and neuroimaging biomarkers of neurodegenerative diseases: a systematic review. Frontiers in Dementia, 5, Article 1912295. https://doi.org/10.3389/frdem.2026.1912295

Image Credits: AI Generated

DOI: 10.3389/frdem.2026.1912295

Keywords: menopause, Alzheimer's disease, neuroimaging, estrogen, dementia, women's health, MRI, PET, Premature, early, biomarkers, neurodegenerative

The timing of this convergence is significant. Women spend decades of their lives post-menopause, and the menopausal transition coincides with a rising burden of chronic conditions such as cardiovascular disease, osteoporosis, and depression. Prescription medication use climbs steeply through midlife, and polypharmacy is increasingly common among older adults. Yet drug trials rarely record menopausal status in a standardized way, and few studies have directly compared drug responses between premenopausal, perimenopausal, and postmenopausal women. Haga’s central argument is that this blind spot may conceal an important source of interindividual variability in drug efficacy and toxicity, one rooted in the interplay between falling estrogen levels and a rapidly remodeling gut microbial community.

The evidence that menopause reshapes the gut microbiome is now substantial. Estrogen receptors are expressed throughout the gastrointestinal tract, where estrogen helps regulate epithelial barrier integrity, mucosal immunity, intestinal permeability, inflammatory signaling, and bile acid metabolism. When ovarian function declines, these effects wane, and microbial communities shift accordingly. Studies have documented menopause-associated changes not only in the gut but also in vaginal, oral, and urogenital microbiomes. One large population study even found that the postmenopausal gut microbiome resembles that of men more closely than that of premenopausal women. These microbial alterations have, in turn, been implicated in conditions ranging from metabolic dysfunction and osteoporosis to depression and hormone-related cancers, suggesting that microbiome remodeling may contribute to the very diseases that drive pharmacotherapy in midlife.

Crucially, the relationship runs in both directions. The gut microbiome contributes to estrogen homeostasis through a collection of microbial genes called the estrobolome, which encodes enzymes capable of deconjugating estrogens in the intestine. After the liver converts circulating estrogens into inactive, water-soluble glucuronides and excretes them into bile, gut bacterial beta-glucuronidases strip off the glucuronic acid moiety, regenerating biologically active estrogens that can be reabsorbed through enterohepatic circulation. This microbial rescue of hormones helps maintain circulating estrogen concentrations despite hepatic metabolism. The functional capacity of the estrobolome varies considerably between individuals and is shaped by age, diet, medication exposure, antibiotic use, obesity, and other lifestyle factors, making it a plausible determinant of how much active hormone any given woman retains.

This same enzymatic pathway provides what the review identifies as the strongest mechanistic bridge between endocrine physiology and pharmacology. Many therapeutic agents undergo hepatic glucuronidation as part of phase II metabolism, producing inactive conjugates that are secreted into bile and delivered to the intestinal lumen. Bacterial beta-glucuronidases can hydrolyze those conjugates just as they do estrogen glucuronides, regenerating the active parent compound within the gut. Depending on the drug, this reactivation can prolong exposure, enhance efficacy, or intensify toxicity. The best-characterized example is the chemotherapy agent irinotecan, in which microbial reactivation of the inactive metabolite SN-38G produces active SN-38 in the colon, causing dose-limiting diarrhea and intestinal injury. Similar mechanisms have been described for nonsteroidal anti-inflammatory drugs, mycophenolate mofetil, morphine, and the osteoporosis drug raloxifene, all of which are commonly used by women in midlife and beyond.

Beyond the estrobolome, the review catalogs several other microbiome-mediated pathways that could interact with menopause-related changes. Gut bacteria possess an extensive enzymatic repertoire that directly metabolizes drugs before absorption or excretion. Classic examples include the inactivation of the cardiac drug digoxin by the bacterium Eggerthella lenta, bacterial activation of the prodrug sulfasalazine in the colon, and microbial metabolism of levodopa used in Parkinson’s disease. Because microbial composition changes after menopause, the abundance and activity of these drug-transforming organisms may shift as well, though the review emphasizes that almost nothing is known about how menopause specifically alters microbial xenobiotic metabolism. This remains an emerging rather than an established mechanism.

Bile acid biology offers another biologically plausible route. The gut microbiome transforms host-derived primary bile acids into secondary bile acids through deconjugation, oxidation, epimerization, and dehydroxylation. Bile acids are far more than digestive detergents; they act as signaling molecules through receptors such as the farnesoid X receptor and TGR5, influencing glucose and lipid metabolism, inflammation, and intestinal barrier integrity. They also affect the absorption of orally administered drugs and regulate the expression of hepatic and intestinal transporters and xenobiotic-metabolizing enzymes. Reviews of the emerging literature suggest that menopause alters both gut microbial composition and bile acid metabolism, but whether these changes translate into clinically meaningful differences in drug pharmacokinetics or pharmacodynamics is still unknown.

Microbial metabolites and immune regulation complete the mechanistic picture, though with even thinner direct evidence. Bacteria produce short-chain fatty acids, indole derivatives, secondary bile acids, trimethylamine, and other bioactive compounds that interact with host receptors and can modulate the expression and activity of cytochrome P450 enzymes, membrane transporters, and nuclear receptors involved in drug disposition. Menopause has been associated with altered short-chain fatty acid production and bile acid profiles, although findings vary across studies. Meanwhile, declining estrogen can independently disrupt intestinal tight junctions, increasing permeability and promoting low-grade inflammation, effects that microbial dysbiosis can amplify. These changes do not metabolize drugs directly, but they may alter intestinal absorption, hepatic metabolism, and susceptibility to adverse drug reactions, and hormonal and microbial factors appear to act synergistically on host physiology.

Haga is careful to note that direct clinical evidence connecting menopause-associated microbiome remodeling with altered drug response remains limited. The strongest data support two independent pillars: menopause changes the gut microbiome, and the gut microbiome influences drug metabolism. Bridging the two will require overcoming significant methodological gaps. Clinical trials rarely assess menopausal status with standardized criteria, microbiome characterization has emphasized taxonomic composition rather than functional capacity, and important modifiers such as menopausal hormone therapy, diet, obesity, and concomitant medications are infrequently integrated into study design. Fecal sampling, which reflects mainly distal colonic luminal communities, may also incompletely capture the mucosa-associated and region-specific microbiota most relevant to drug disposition. The contributions of non-bacterial microbial components, including the virome, mycobiome, and archaeome, remain essentially unexplored.

The path forward, the review argues, lies in integrated longitudinal studies that follow women across the menopausal transition with repeated measurements of hormones, microbiome function, medications, and clinical outcomes. Because microbial functional capacity, measured through beta-glucuronidase activity, xenobiotic-metabolizing enzymes, bile acid profiles, and metatranscriptomics or metabolomics, may predict medication response better than species lists alone, functional profiling should become a priority. With menopausal hormone therapy now increasingly used in appropriately selected women, researchers must also determine whether its route, formulation, timing, and duration modify the gut microbiome or microbiome-mediated drug responses. Ultimately, intervention trials using diet, probiotics, prebiotics, or selective microbial enzyme inhibitors would provide the strongest evidence for causality. For now, the review concludes, microbiome-informed prescribing is not ready for the clinic, but the framework it outlines could eventually help explain why two women with identical prescriptions and similar health profiles can experience dramatically different therapeutic outcomes, and it positions menopausal status as a variable that precision medicine can no longer afford to ignore.

Subject of Research: Menopause-associated gut microbiome remodeling and its influence on drug metabolism and therapeutic response

Article Title: Menopause-associated gut microbiome remodeling and pharmacomicrobiomics: emerging mechanisms influencing drug response

Article References: Haga, S. B. (2026). Menopause-associated gut microbiome remodeling and pharmacomicrobiomics: emerging mechanisms influencing drug response. Frontiers in Microbiomes, 5, Article 1953547. https://doi.org/10.3389/frmbi.2026.1953547

Image Credits: AI Generated

DOI: 10.3389/frmbi.2026.1953547

Keywords: menopause, gut microbiome, pharmacomicrobiomics, estrogen, estrobolome, beta-glucuronidase, drug metabolism, bile acids, microbial metabolites, intestinal barrier, precision medicine, polypharmacy

NETosis is a spectacular and violent form of cell death. When a neutrophil is activated, it decondenses its own nucleus, mixes its DNA with cytoplasmic and granule proteins, and casts the whole tangle outward as a web-like structure that can snare and neutralize pathogens. The process is a cornerstone of innate immunity, but it has a dark side. In rheumatoid arthritis, proteins externalized during NETosis can become citrullinated, sparking the generation of anti-citrullinated protein antibodies, or ACPA, the hallmark autoantibodies of the disease. NETs correlate with disease activity in RA patients, and in systemic lupus erythematosus, a relative inability to degrade NETs has been linked to a higher incidence of lupus nephritis, one of the most serious complications of the disease.

What makes the new findings especially provocative is the demographic backdrop. Autoimmune diseases in which NETs are implicated strike women far more often than men, and the skew is most extreme during the premenopausal years. Rheumatoid arthritis shows a female-to-male ratio of roughly 5:1 in premenopausal women, and lupus reaches an astonishing 10:1. Neutrophils from premenopausal women display a more mature and responsive phenotype than male neutrophils, with a correspondingly greater propensity for NET formation, and estrogen itself can drive this pro-NETotic behavior. That observation placed oral contraceptives squarely in the crosshairs of the Colorado team, led by Daniele Marcy and M. Kristen Demoruelle, because the pill commonly induces anovulation and thereby lowers total systemic estrogen exposure.

The researchers drew on the Studies of the Etiology of Rheumatoid Arthritis, or SERA, an observational project running since 2005 that follows first-degree relatives of people with established RA alongside healthy community controls. From stored plasma samples, the team assembled three groups of premenopausal women: a derivation cohort of 77 healthy women, a validation cohort of 87 healthy women, and a cohort of 104 women at elevated risk for RA because a first-degree relative had the disease. All participants completed detailed questionnaires on contraceptive, pregnancy, and smoking histories, and blood was drawn in EDTA tubes, processed within 30 minutes, and stored at minus 80 degrees Celsius until batch testing.

To gauge NETosis, the team measured plasma calprotectin, a heterodimer of the alarmin proteins S100A8 and S100A9 that are highly abundant in the neutrophil cytoplasm and released during NET formation. Calprotectin is a well-established marker of neutrophil activation and correlates with inflammation in NET-associated diseases, and because it can be quantified with a widely available commercial ELISA kit, the assay offers low inter-assay variability and a plausible path into routine clinical care. Importantly, the researchers excluded anti-CCP-positive individuals, since ACPA can independently induce NETosis and would muddy the interpretation. Laboratory technicians were blinded to each sample’s contraceptive status.

The results were strikingly consistent. Among healthy women in the derivation cohort, current pill users had a mean calprotectin level of 0.99 micrograms per milliliter compared with 1.38 in never or prior users, a difference that reached statistical significance at p equals 0.016. The validation cohort reproduced the pattern, with 0.9 versus 1.4 micrograms per milliliter and a p value of 0.001. In the at-risk relatives, current users again measured lower, at 1.19 versus 1.74 micrograms per milliliter, p equals 0.017. In multivariable linear regression models adjusting for age, ever smoking, and ever pregnancy—variables previously linked to NET levels—the association held, with borderline significance in the derivation cohort and a highly significant result in the validation cohort, where pill users averaged 0.56 micrograms per milliliter less calprotectin. Among the at-risk women, the adjusted difference was 0.73 micrograms per milliliter.

Notably, the effect did not appear to accumulate over time. There was no correlation between calprotectin levels and the duration of pill use, nor between calprotectin and the years elapsed since discontinuation among prior users. The authors argue this fits a model in which OCP-induced anovulation suppresses the high peri-ovulatory estradiol peaks that push neutrophils toward a NET-prone phenotype, an effect that begins shortly after initiation and reverses quickly upon stopping. When the team could confirm formulations through medical chart review, all 36 women documented were taking low-dose estradiol preparations of 0.035 milligrams or less, and estradiol dosage itself showed no correlation with calprotectin levels.

The numbers also sit sensibly within known biology. Mean calprotectin among healthy never or prior pill users, around 1.4 micrograms per milliliter, falls toward the upper end of the typical published range of 0.1 to 1.5, while the at-risk cohort’s never users averaged a modestly elevated 1.74. By contrast, patients with active rheumatoid arthritis commonly show calprotectin levels in the range of 10 to 50 micrograms per milliliter, underscoring that the study captured differences in a healthy or very early at-risk state rather than florid inflammation. The choice of EDTA-preserved plasma rather than serum also matters, since clotting during serum generation can activate neutrophils ex vivo and artificially inflate measured calprotectin.

The authors are careful about what the study can and cannot claim. As a cross-sectional analysis, it demonstrates association, not causation, and calprotectin release is not exclusive to NETosis—neutrophil necrosis and degranulation can also contribute. The team did not directly measure estradiol levels or confirm ovulatory status with luteinizing hormone surges, and no participants developed clinical RA during follow-up, precluding direct assessment of whether reduced NETosis actually mediates the lower RA risk previously reported in pill users. Still, multiple epidemiologic studies, including the Swedish EIRA study, have linked oral contraceptive use to reduced RA risk and to lower positivity for rheumatoid factor, and the new data offer a candidate mechanism: dampening NET formation and the citrullinated antigens it generates during a critical window of immune priming.

Future work, the researchers say, should extend these observations to women with established RA and lupus, examine neutrophil function before and after pill initiation in vivo, and test whether other hormonal contraceptives differing in estrogen dose, formulation, and route of administration produce similar effects. The study was funded by the National Institutes of Health and the University of Colorado Anschutz Ludeman Family Center for Women’s Health Research, and it appears in Frontiers in Lupus. If confirmed longitudinally, the findings could reframe a daily pill taken by millions as an unexpected modulator of innate immunity—one that may quietly influence which women’s neutrophils never fire their traps at all.

Subject of Research: Immunology

Article Title: Oral contraceptive pill Use is associated with lower levels of plasma calprotectin in premenopausal women

Article References: Marcy, D., Maretz, C., Sturm, K., Lugo, C., Deane, K. D., Holers, V. M., Norris, J. M., Zell, J., & Demoruelle, M. K. (2026). Oral contraceptive pill Use is associated with lower levels of plasma calprotectin in premenopausal women. Frontiers in Lupus, 4, Article 1819508. https://doi.org/10.3389/flupu.2026.1819508

Image Credits: AI Generated

DOI: 10.3389/flupu.2026.1819508

Keywords: oral contraceptives, calprotectin, NETosis, neutrophil extracellular traps, rheumatoid arthritis, lupus, autoimmune disease, estrogen, premenopausal women, immunology, women's health, biomarkers