Early menarche in association with ovarian reserve and biological aging in young adults: a cross-sectional study

Age at menarche has declined in many populations, but whether earlier menarche is related to ovarian reserve markers and biological aging in young adulthood remains unclear. In this cross-sectional study, we compared 82 women with early menarche (<12 years) and 92 women with normal menarche (12-13.5 years), all aged 18-25 years, from Anhui Province, China. Serum anti-Müllerian hormone (AMH), follicle-stimulating hormone (FSH), luteinizing hormone and estradiol (E2) were measured; antral follicle count (AFC) and ovarian volume were assessed by transabdominal ultrasound; and biological age was estimated using the Klemera-Doubal method (KDM-BA) and Phenotypic Age (PhenoAge). After adjustment for potential confounders, early menarche was associated with lower AMH (-15.5%, 95% CI: -26.8% to -2.4%) and AFC (-6.2%, 95% CI: -11.4% to -0.8%), higher FSH (22.1%, 95% CI: 5.5% to 41.3%) and E2 (25.7%, 95% CI: 6.5% to 48.3%), and greater KDM-BA acceleration (0.75 years, 95% CI: 0.04 to 1.46), but not with PhenoAge acceleration. These associations were modest: menarche group explained only 1.4%-4.1% of the variance in these outcomes. Early menarche is associated with small differences in ovarian reserve markers and biological age in young women; however, on its own it is unlikely to indicate a clinically meaningful reduction in reproductive potential.