The research team, led by investigators from Peking University’s School of Public Health in collaboration with the Meinian Institute of Health, analyzed records from 10,748,391 adults who underwent health examinations between 2017 and 2023. Every included participant had complete thyroid function results covering the three core laboratory measures used to define thyroid status: serum thyroid-stimulating hormone (TSH), free triiodothyronine (FT3), and free thyroxine (FT4). This trio of hormones allows clinicians to distinguish an overactive gland from an underactive one, and to separate overt disease, in which hormone levels are clearly abnormal, from subclinical disease, in which the pituitary’s regulatory signal is disturbed while the circulating thyroid hormones themselves remain within reference limits.

Using this framework, the researchers classified participants into four diagnostic categories. Overt hyperthyroidism, in which TSH is suppressed and thyroid hormones are elevated, had a weighted prevalence of 0.76 percent. Subclinical hyperthyroidism, marked by suppressed TSH with normal hormone levels, was slightly more common at 0.82 percent. Overt hypothyroidism, in which TSH rises while thyroid hormones fall, affected 0.58 percent of the population. The standout figure was subclinical hypothyroidism, defined by elevated TSH with normal free thyroid hormones, which reached a weighted prevalence of 8.27 percent. Taken together, the findings suggest that roughly one in ten Chinese adults carries some form of thyroid dysfunction, the vast majority of it silent or minimally symptomatic.

The demographic patterns were consistent with long-standing clinical observations but now quantified at unprecedented scale. Thyroid dysfunction was more prevalent in women than in men across all categories, reflecting the well-documented female predominance of autoimmune thyroid disease. Prevalence also rose with age for most conditions, with the notable exception of overt hyperthyroidism, which did not follow the same age-related climb. Socioeconomic geography mattered as well: people living in cities with lower gross domestic product levels showed higher rates of thyroid dysfunction, a gradient that the authors suggest may reflect differences in iodine nutrition, environmental exposures, diagnostic access, or broader patterns of chronic disease burden.

Perhaps the most striking feature of the study is its geographic resolution. Subclinical hyperthyroidism was concentrated in coastal regions of China, while both overt and subclinical hypothyroidism were more widely distributed across inland provinces. This coastal-inland divide echoes historical patterns of iodine intake, since coastal populations typically consume more iodine-rich seafood while inland areas have historically experienced both iodine deficiency and, in some regions, excessive iodine from drinking water and local food supplies. Because both too little and too much iodine can disrupt thyroid function, these regional gradients provide public health authorities with a geographic roadmap for targeted screening and nutritional intervention.

Beyond prevalence, the study’s central contribution is its systematic examination of multimorbidity. Rather than asking whether thyroid dysfunction is linked to a single disease, the investigators assessed associations with 21 medical conditions spanning multiple organ systems. The results reveal two distinct clinical signatures. Hyperthyroidism, whether overt or subclinical, was primarily associated with a fast resting heart rate, abnormal liver enzymes, decreased high-density lipoprotein cholesterol, and hyperglycemia. These associations make physiological sense: excess thyroid hormone accelerates cardiac rhythm, increases metabolic turnover that can strain the liver, and reshapes lipid and glucose metabolism in ways that mimic or exacerbate metabolic syndrome.

Hypothyroidism told a different story. Both overt and subclinical forms were more closely associated with abnormal liver enzymes, impaired renal function, dyslipidemia, obesity, and fatty liver disease. An underactive thyroid slows lipid clearance, promoting elevated cholesterol and triglycerides; it reduces metabolic rate, favoring weight gain and hepatic fat accumulation; and it can reduce kidney perfusion and glomerular filtration, blurring the boundary between endocrine and renal pathology. The convergence of hypothyroidism with fatty liver and dyslipidemia is particularly relevant for China, where non-alcoholic fatty liver disease and cardiometabolic risk factors have been rising sharply alongside economic development and dietary change.

The study also uncovered sex-specific differences in how subclinical thyroid dysfunction relates to atherosclerotic markers, specifically increased carotid intima-media thickness and the presence of carotid plaques, both established indicators of subclinical vascular disease. This finding suggests that even mild thyroid hormone disturbances may participate in early vascular remodeling differently in men and women, potentially through effects on blood pressure, lipid profiles, inflammation, or heart rate. Because carotid intima-media thickness predicts future cardiovascular events, the observation raises the possibility that subclinical thyroid status could help stratify cardiovascular risk, although the cross-sectional design of the study cannot establish whether thyroid dysfunction causes vascular change or merely co-occurs with it.

Methodologically, the study demonstrates the power of big data resources in epidemiology. By mining an existing national health check-up database rather than mounting a bespoke survey, the team achieved a sample size and geographic coverage that would be prohibitively expensive through conventional means. The authors describe this approach as a rapid and cost-effective complement to nationally representative studies. The trade-offs are equally clear: health check-up populations skew toward urban, insured, and health-conscious individuals, and the cross-sectional design captures a snapshot rather than tracking how thyroid dysfunction develops over time. Weighted prevalence estimates help correct for some sampling imbalances, but the figures should be read as describing the examined population rather than the entire nation with survey-grade precision.

The clinical implications are nonetheless substantial. With subclinical hypothyroidism affecting more than eight percent of adults, and with thyroid dysfunction consistently co-occurring with cardiovascular, metabolic, hepatic, and renal abnormalities, the authors argue for continued surveillance of thyroid health and for patient-centered, multidisciplinary management strategies at the health system level in China. In practice, that means a person diagnosed with hypothyroidism should not simply receive a thyroid hormone prescription in isolation; their lipid profile, liver enzymes, kidney function, weight, and cardiovascular risk deserve coordinated attention. Conversely, patients presenting with dyslipidemia, fatty liver, or unexplained tachycardia may merit thyroid function testing. As China’s population ages and cardiometabolic disease burden grows, this study provides the quantitative foundation for integrating one of the body’s master metabolic regulators into the broader agenda of chronic disease prevention.

Subject of Research: Prevalence and multimorbidity patterns of thyroid dysfunction among adults in China

Article Title: Prevalence and multimorbidity patterns of thyroid dysfunction in Chinese adults

Article References: Shen, D., Man, S., Zu, Y., Yang, X., Deng, Y., Chen, S., Yu, C., Li, L., Wang, B., Pan, H., & Lv, J. (2026). Prevalence and multimorbidity patterns of thyroid dysfunction in Chinese adults. BMC Endocrine Disorders. https://doi.org/10.1186/s12902-026-02589-0

Image Credits: AI Generated

DOI: 10.1186/s12902-026-02589-0

Keywords: thyroid dysfunction, hypothyroidism, hyperthyroidism, subclinical hypothyroidism, multimorbidity, epidemiology, China, TSH, thyroid-stimulating hormone, fatty liver, dyslipidemia, cardiovascular risk

The thyroid is a small, butterfly-shaped gland at the base of the neck, but its influence during pregnancy is enormous. Its hormones help regulate fetal brain development, metabolic rate, and cardiovascular adaptation to gestation. In early pregnancy, the placental hormone human chorionic gonadotropin suppresses TSH, the pituitary signal that tells the thyroid to work, which is why pregnancy-specific reference ranges for TSH are lower than those used in the general population. When the gland cannot keep pace, TSH rises, a pattern often labeled subclinical hypothyroidism when free thyroxine remains normal. Whether mild elevations of this signal harm the mother’s mental state has remained contested, with previous studies producing a patchwork of conflicting results.

Researchers led by Havva Betul Bacak of the University of Health Sciences Gaziosmanpasa Training and Research Hospital in Istanbul designed a prospective observational cohort to address that question directly. Between November 2025 and January 2026, they recruited 208 pregnant women attending antenatal care at their institution. Before any clinical examination or blood draw, each participant completed a battery of well-validated self-report questionnaires: the Beck Depression Inventory, the Beck Anxiety Inventory, the Arizona Sexual Experiences Scale, and the 13-item Turkish Short-Form Quality of Life questionnaire. Completing the psychometric instruments before the medical evaluation was a deliberate design choice, intended to prevent a physician’s assessment or discussion of thyroid results from coloring the women’s self-reported emotional state.

After predefined exclusions, the analytic sample settled at 192 women. The investigators excluded anyone with autoimmune thyroid disease, current thyroid medication use, and other conditions that could confound thyroid physiology, and women whose TSH measured at or above 2.5 mIU/L were referred for endocrinology consultation as part of standard care. The final cohort split into 102 women with TSH below 2.5 mIU/L and 90 women at or above that cutoff. Critically, the two groups were statistically indistinguishable in age, gestational age, number of previous pregnancies, parity, and body mass index, which strengthens the interpretation that differences in psychological scores were not simply reflections of different demographic profiles.

The headline result was clear and consistent for mood. Median scores on the Beck Depression Inventory were 13.0 in the higher-TSH group versus 10.0 in the lower-TSH group, a difference that reached statistical significance with a p-value of 0.002. The Beck Anxiety Inventory told a similar story, with median scores of 11.0 versus 8.0 and a p-value of 0.009. While these are moderate symptom scores rather than diagnoses of major depressive disorder, the direction and consistency of the shift across two independent instruments is notable. Perinatal depression affects roughly one in seven women worldwide by some estimates, and anxiety disorders in pregnancy are similarly common, so any physiological marker that tracks with symptom burden is clinically interesting even if the effect is modest.

Equally interesting was what did not change. Scores on the sexual function scale and the quality-of-life instrument showed no statistically significant differences between the TSH groups, with p-values of 0.400 and 0.068 respectively. This dissociation is intriguing because mood, sexual function, and quality of life are typically intertwined. The authors suggest that quality-of-life changes may emerge at higher degrees of thyroid dysfunction, or that pregnancy itself dampens the measurable influence of mild thyroid signals on sexuality, since expectant mothers report sexual difficulties at high rates regardless of thyroid status. The mood findings, by contrast, appear to register the thyroid signal more sensitively.

Beyond the fixed 2.5 mIU/L cutoff, the researchers performed exploratory pairwise analyses using finer TSH strata. The first detectable separation in depression scores appeared between women below 2.5 mIU/L and those in the 2.5 to below 4.5 mIU/L band, with a p-value of 0.007, while comparisons between the 2.5 to below 4.5 and the 4.5-and-above groups were not significant for any of the four measures. In complementary analyses treating TSH as a continuous variable, higher maternal TSH was weakly but monotonically associated with higher depression and anxiety scores and lower quality of life, with no evidence of a nonlinear or threshold-like relationship. In other words, the data hint that the psychological gradient may begin at the lower end of the elevated range rather than accumulating only after TSH climbs far above it.

The authors are careful, and appropriately so, about what these findings cannot establish. The study did not measure free thyroxine or thyroid peroxidase antibodies, two variables that international guidelines consider essential for classifying thyroid dysfunction during pregnancy. It relied on a fixed pragmatic TSH cutoff rather than trimester-specific reference intervals, which recent individual-participant-data meta-analyses have shown vary substantially across populations and assay methods. The statistical comparisons were unadjusted, without multivariable models accounting for potential confounders, and the single-center design limits generalizability. The team explicitly frames the results as exploratory and hypothesis-generating, not as evidence of an independent or causal association between TSH and mental health. Reverse causation remains plausible too: women experiencing more depressive or anxious symptoms may have different neuroendocrine profiles for reasons unrelated to thyroid pathology.

Nevertheless, the study lands in an active and consequential scientific conversation. The American Thyroid Association, the American College of Obstetricians and Gynecologists, and other professional bodies have long disagreed about whether a 2.5 mIU/L TSH threshold should trigger treatment, and large trials of levothyroxine therapy for mild thyroid abnormalities in pregnancy have generally failed to show clear benefits for cognitive or obstetric outcomes. Prior research has linked antenatal thyroid measures to postpartum depression, and meta-analyses have connected overt hypothyroidism with female sexual dysfunction, but data on subclinical elevations and psychological well-being during gestation itself have been sparse and inconsistent. By collecting psychometric data prospectively, before clinical interaction, and by examining sexual function and quality of life alongside mood, the Turkish team has added a rarely explored angle to the debate.

The practical implications, for now, are more about research design than treatment. The monotonic, weak association between TSH and mood symptoms suggests that if a real psychological effect of mild thyroid underactivity in pregnancy exists, it is subtle and distributed across the upper range of normal rather than concentrated above any sharp threshold. That pattern argues for studies that measure free hormones and antibodies, apply trimester-specific reference intervals, adjust for psychosocial confounders, and follow women into the postpartum period, where the consequences of untreated perinatal mood disorders are best documented. In the meantime, the study offers clinicians a reminder that the familiar TSH value on a prenatal panel may be worth reading not only as a metabolic number but as a potential, if still unproven, window into the emotional landscape of pregnancy.

Subject of Research: Maternal thyroid-stimulating hormone levels and their association with depression, anxiety, sexual function, and quality of life during pregnancy.

Article Title: Association of Maternal Thyroid-stimulating Hormone Levels with Psychological Well-being, Sexual Function, and Quality of Life During Pregnancy

Article References: Bacak, H. B., Ketenci Gencer, F., Coskun, E. S., Irice, F., Aciyiyen, Y., Terkan, H., Celikoglu Berker, E., Deligozoglu, S., Kumbasar, S., & Salman, S. (2026). Association of Maternal Thyroid-stimulating Hormone Levels with Psychological Well-being, Sexual Function, and Quality of Life During Pregnancy. Reproductive Sciences. https://doi.org/10.1007/s43032-026-02206-4

Image Credits: AI Generated

DOI: 10.1007/s43032-026-02206-4

Keywords: pregnancy, thyroid-stimulating hormone, TSH, depression, anxiety, sexual function, quality of life, subclinical hypothyroidism, prenatal care, Reproductive Sciences, Association, Maternal