anti-Müllerian hormone

AMH is a member of the TGF-β superfamily. In male fetal development, Sertoli cells secrete AMH starting around week 8, causing regression of the Müllerian (paramesonephric) ducts, which would otherwise develop into the fallopian tubes, uterus, cervix, and upper vagina. This action works alongside testosterone (which stimulates Wolffian/mesonephric duct development into male internal genitalia) and dihydrotestosterone (DHT, which drives external genitalia virilization) to ensure proper male sexual differentiation. AMH acts locally (paracrine) rather than systemically, explaining why unilateral gonadal defects can result in asymmetric persistence of Müllerian structures. Clinically, deficiency or receptor mutations in the AMH pathway cause Persistent Müllerian Duct Syndrome (PMDS)—a form of male pseudohermaphroditism where genetically and phenotypically male individuals (46,XY) retain Müllerian derivatives (uterus, fallopian tubes) alongside normal male external genitalia and testes, often discovered incidentally during hernia repair (containing a uterus, historically called 'hernia uteri inguinale'). This contrasts with Swyer syndrome (XY gonadal dysgenesis) where both AMH and testosterone are absent/deficient due to lack of functional testes, leading to a female phenotype with retained Müllerian structures. In females, granulosa cells of small antral and preantral follicles produce AMH, and serum AMH levels correlate with the size of the growing follicle pool, making it a valuable clinical marker of ovarian reserve—used in fertility evaluations and to predict response to ovarian stimulation in IVF. AMH levels decline with age and are markedly elevated in polycystic ovary syndrome (PCOS) due to increased numbers of small antral follicles. AMH-producing granulosa cell tumors can also cause elevated AMH levels and are associated with precocious puberty or virilization depending on hormone secretion patterns.