anti-Mullerian hormone

Anti-Mullerian hormone (AMH) is best known as a gauge of how many eggs a woman has in reserve. Think of it as a dipstick for the ovary: it does not measure today's cycle so much as the overall size of the standing pool of small follicles waiting in the wings.

AMH has two distinct lives. In the male fetus it is the hormone that causes the Mullerian ducts — the precursors of the uterus and fallopian tubes — to regress, which is why it was first named for that effect. In adult women it is secreted by the granulosa cells of small growing follicles, and because the number of those follicles reflects the remaining egg pool, blood AMH falls steadily with age and approaches undetectable levels around menopause.

Clinically, AMH is valued because, unlike many reproductive hormones, it stays relatively stable across the menstrual cycle, making it a convenient single-draw test of ovarian reserve to predict response to fertility treatment. An important caveat: AMH estimates the quantity of eggs, not their quality or a woman's ability to conceive naturally, and it is often elevated in polycystic ovary syndrome, where small follicles are unusually numerous.