Anti-Müllerian hormone is produced by ovarian granulosa cells in women and Sertoli cells in men. It's the cleanest non-cycle-dependent marker of ovarian reserve.
Mechanism — Reflects the size of the resting follicle pool. Declines through reproductive lifespan, approaching zero at menopause. In men, AMH is a marker of testicular function and prepubertal Sertoli cell activity.
Lab range — Female fertility relevance: above 1.0 ng/mL is normal for reproductive age; under 1.0 ng/mL suggests diminished reserve; under 0.5 ng/mL is low. Can be drawn any cycle day.
Caveats — AMH predicts response to fertility treatment, not natural conception likelihood. Hormonal contraception can suppress it modestly.