The test measures a hormone called anti – Müllerian hormone (AMH). This hormone is very important during the development of the male foetus as it is essential for the formation of male reproductive organs.
In males, AMH is generated within cells in the testes. AMH is detectable at birth in males and levels rise rapidly in infancy. After puberty, the levels of AMH decline in men.
In females, small amounts of AMH are produced by developing follicles in the ovaries. At birth and in childhood the level of AMH in girls is very low, but increases significantly at puberty reaching a peak in early adulthood. As women age, the number of follicles (which produce AMH) decreases and so the level of AMH declines and becomes undetectable after the menopause. AMH levels in women therefore reflect the declining ovarian function, and its measurement is said to indicate ovarian reserve.