Estradiol Emerges as a Surprising Early Clue to a Rare Infant Hormone Disorder

A hormone long associated with female biology may hold the key to catching a rare and easily missed male hormonal disorder in the first years of life. New research from the Children’s Hospital Affiliated to Zhengzhou University, published in BMC Pediatrics, suggests that estradiol, a form of estrogen, could serve as a valuable adjunctive marker for diagnosing congenital hypogonadotropic hypogonadism, or CHH, in male infants and toddlers. The finding is striking because estradiol is rarely the first molecule clinicians think of when evaluating underactive testicular function in baby boys, yet the study found it outperformed the traditional gonadotropins in diagnostic accuracy across two distinct age windows.

Congenital hypogonadotropic hypogonadism is a condition in which the hypothalamic-pituitary-gonadal axis, the hormonal circuit that governs sexual development, fails to activate properly. In affected children, the hypothalamus does not release adequate gonadotropin-releasing hormone, or the pituitary gland fails to respond to it, leaving the gonads without the signals they need to mature. The result is gonadal insufficiency and abnormalities of the external genitalia, including cryptorchidism and micropenis, which are often the first visible clues. Because the disorder is rare and its signs can be subtle in infancy, diagnosis is frequently delayed, sometimes until puberty fails to arrive, by which point critical windows for treatment and bone and reproductive development may have been compromised.

The challenge for pediatricians is that there is a natural period when diagnosis is both possible and difficult. Shortly after birth, male infants experience what researchers call mini-puberty, a transient surge of activity along the hypothalamic-pituitary-gonadal axis that occurs roughly from birth to about six months of age. During this window, luteinizing hormone, follicle-stimulating hormone, testosterone, and other sex hormones normally rise to levels approaching those of puberty before settling back to low childhood values. Mini-puberty offers clinicians a rare biochemical opportunity to interrogate the axis in a baby. But in children between six months and three years, the axis goes quiet, and the usual hormone signals fall to levels that are hard to interpret, making the diagnostic window narrow and the interpretation tricky.

To explore whether additional markers could sharpen early diagnosis, the research team led by Dongxia Fu, Xue Wu, Huizhen Wang, Yongxing Chen, and corresponding author Haiyan Wei conducted a case-control study of male infants and toddlers with congenital hypogonadotropic hypogonadism who were hospitalized between January 1, 2018, and December 31, 2019. They enrolled 25 affected boys and divided them into two age groups: those aged six months or younger, capturing the mini-puberty window, and those between six months and three years, when the axis is normally quiescent. For comparison, they recruited healthy controls matched at a ratio of four controls per case, allowing robust statistical comparison across physical examination findings, biochemical indices, sex hormone levels, anti-Müllerian hormone, and inhibin B.

The analytical strategy centered on comparing these measurements between the affected and healthy groups and then testing which markers best discriminated the two. The researchers used receiver operating characteristic, or ROC, analysis, a standard statistical technique that evaluates how well a test separates diseased from healthy individuals. The area under the ROC curve, or AUC, ranges from 0.5, meaning no better than chance, to 1.0, meaning perfect discrimination. Values above 0.9 are generally considered excellent. When the team applied this framework, three molecules stood out as factors associated with CHH: anti-Müllerian hormone, inhibin B, and estradiol.

The headline result concerns estradiol. In the group of infants aged six months or younger, estradiol achieved an area under the curve of 0.951, with a diagnostic cutoff of 9.79 picograms per milliliter. In the older group of children between six months and three years, the area under the curve was 0.939, with a cutoff of 5.55 picograms per milliliter. In both age bands, estradiol showed the strongest diagnostic efficacy of any marker tested. Notably, the study found no statistically significant differences in diagnostic efficacy among luteinizing hormone, follicle-stimulating hormone, estradiol, inhibin B, and anti-Müllerian hormone when compared directly, suggesting that estradiol performs at least as well as the established gonadotropins and Sertoli cell markers rather than replacing them outright.

Why would estradiol, an estrogen, carry diagnostic information about underactive testes in boys? The biology is more intertwined than the name suggests. In males, a substantial fraction of circulating estradiol is produced through aromatization, the enzymatic conversion of testosterone into estradiol in peripheral tissues, and the testes themselves contribute directly. When the hypothalamic-pituitary-gonadal axis fails to fire during mini-puberty, testosterone production stays low, and with it the substrate for estradiol production. Low estradiol in a baby boy during mini-puberty is therefore a downstream echo of the same upstream failure that suppresses luteinizing hormone and follicle-stimulating hormone signaling. In the older toddler group, where baseline hormone levels are naturally low in all children, the estradiol cutoff shifts downward to 5.55 picograms per milliliter, reflecting the quieter hormonal milieu but retaining strong discriminatory power.

The study’s other two standout markers, anti-Müllerian hormone and inhibin B, are both products of Sertoli cells, the nurse cells of the seminiferous tubules that support developing germ cells. Anti-Müllerian hormone is responsible for regressing the Müllerian ducts during male embryonic development and remains a sensitive readout of Sertoli cell activity throughout childhood. Inhibin B, which feeds back on the pituitary to regulate follicle-stimulating hormone, likewise reflects functional testicular tissue. In congenital hypogonadotropic hypogonadism, the gonads are structurally capable but chronically understimulated, and both markers register the deficit. The authors found that the combination of low anti-Müllerian hormone and low inhibin B, interpreted alongside the estradiol cutoffs of 9.79 picograms per milliliter for mini-puberty and 5.55 picograms per milliliter for the six-month to three-year range, significantly improved early detection compared with any single measure alone.

The practical implications reach beyond the laboratory. Distinguishing congenital hypogonadotropic hypogonadism from other causes of gonadal dysfunction in infancy, such as androgen insensitivity syndrome or 5-alpha-reductase deficiency, both of which can present with ambiguous or undermasculinized genitalia, is a genuine diagnostic puzzle. Whole-exome sequencing can identify causative mutations, but genetic results take time and not all cases yield a clear answer. A panel of blood-based markers that can be drawn during a routine hospitalization, interpreted with age-specific cutoffs, and combined with clinical findings could shorten the path to diagnosis, allow earlier initiation of appropriate hormonal therapy, and spare families months or years of uncertainty. The authors position estradiol specifically as an adjunctive marker, a supporting player that adds confidence when read together with anti-Müllerian hormone and inhibin B rather than a standalone test.

Certain caveats frame the findings appropriately. The study involved 25 affected children from a single center, and the affected group was divided into two age subgroups, so the per-group sample sizes are modest, and the reported areas under the curve will need validation in larger, multi-center cohorts before the cutoffs enter routine practice. The study also focused exclusively on male patients, since congenital hypogonadotropic hypogonadism in this cohort presented with gonadal dysfunction and genital abnormalities in boys. Nevertheless, the work opens a genuinely new angle on a stubborn diagnostic problem: it demonstrates that a hormone conventionally associated with ovarian function carries independent, quantifiable diagnostic information about the failing male axis in the very age window when clinicians have the best and perhaps only chance to act. If larger studies confirm the cutoffs, a simple estradiol measurement, already available in most clinical laboratories, could become part of the standard early workup for boys with suspicious genital findings, turning a fleeting developmental window into a genuine diagnostic opportunity.

Subject of Research: Estradiol as an adjunctive diagnostic marker for congenital hypogonadotropic hypogonadism in male infants and toddlers

Article Title: Estradiol as a potential adjunctive marker for congenital hypogonadotropic hypogonadism in infants and toddlers

Article References: Fu, D., Wu, X., Wang, H., Chen, Y., & Wei, H. (2026). Estradiol as a potential adjunctive marker for congenital hypogonadotropic hypogonadism in infants and toddlers. BMC Pediatrics. https://doi.org/10.1186/s12887-026-07022-y

Image Credits: AI Generated

DOI: 10.1186/s12887-026-07022-y

Keywords: congenital hypogonadotropic hypogonadism, estradiol, anti-Müllerian hormone, inhibin B, mini-puberty, hypothalamic-pituitary-gonadal axis, pediatric endocrinology, diagnostic markers, luteinizing hormone, follicle-stimulating hormone, infants, BMC Pediatrics