Anti-Müllerian hormone (AMH) is a hormone produced by reproductive tissues, including the testicles in males and the ovaries in females. The role of AMH and the amount normally present varies depending upon sex and age. This test measures AMH in the blood.
Very early in the development of a baby boy, AMH is produced by the testicles, inhibiting the development of female reproductive organs while promoting the development of other male reproductive organs. In boys, the level of AMH remains high until puberty, when it begins to taper off.
In girls, low levels of AMH are produced, thus allowing the development of female reproductive structures. The AMH level in young girls remains low until puberty, when the ovaries begin to produce it and levels increase. AMH will then steadily decline in women over their reproductive years, becoming very low and eventually undetectable after menopause.
AMH is important for a woman during her childbearing years. At birth, a female has about one million eggs (oocytes), which then decrease naturally in number during childhood to about 500,000. Only a tiny number of these remaining eggs will go through follicle maturation – one at a time as part of a woman’s monthly menstrual cycle. AMH has a balancing effect on the monthly cyclical actions of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) during the process of egg maturation and release (ovulation). The amount of AMH present is a reflection of this follicular growth.
Studies have shown that the AMH level may be useful in determining a woman’s remaining egg maturation potential (ovarian reserve) and her likelihood of conceiving. AMH declines over time during childbearing years, drops significantly as menopause approaches, and typically becomes almost undetectable after menopause. Determining the AMH level may be useful in evaluating a woman’s current fertility status and may predict the onset of menopause.
Elevated AMH levels have been associated with a condition affecting the ovaries known as polycystic ovary syndrome (PCOS). The excess follicles that occur in this syndrome produce abnormally large amounts of AMH.
AMH also plays a vital part in sexual differentiation in the fetus. During the first few weeks of pregnancy, a developing baby has the potential to develop either male or female reproductive organs. Production of AMH and androgens by the two testicles that are present in a baby boy inhibits development of female reproductive organs (the Müllerian ducts found in both male and female fetuses) and promotes the formation of other male reproductive organs. If a sufficient amount of AMH is not available or absent during this process, then both male and basic female organs may develop. A baby born with ambiguous genitalia may not be instantly recognized as either male or female.
AMH may be elevated in some ovarian tumors (benign or cancerous). If a tumor produces the hormone, then the AMH test can be used as a tumor marker to monitor the effectiveness of treatment and to monitor for recurrence.
