AMH (Anti-Mullerian hormone) | Pathology Tests Explained

This test measures anti-Mullerian hormone (AMH) in the blood. It is often used along with other hormone tests such as oestradiol, progesterone and FSH to assess a woman's ability to produce eggs that can be fertilised for pregnancy. The total number of healthy, immature eggs in the ovaries is known as the ovarian reserve. A lower level of AMH indicates there are fewer eggs remaining. AMH levels gradually decline as a woman ages and as the number of eggs decreases. This has implications for a woman's ability to become pregnant and her likely responsiveness to in vitro fertilisation (IVF) treatment.

An AMH test can be helpful if you are concerned about your future fertility and want to consider either freezing your eggs or trying for a pregnancy sooner rather than later. AMH is also one of several tests used to evaluate new-born babies who are not clearly male or female due to underdevelopment of their external sex organs.

What is being tested?

This test measures anti-Mullerian hormone (AMH) in the blood. AMH is a hormone produced by reproductive tissues; it is produced in the testicles in males and in the ovaries in females. The role of AMH and the amount normally present varies depending upon sex and age.

Very early in the development of a male foetus, 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 about 2 to 6 years of age, when it begins to taper off, and then it drops considerably at puberty.

Since female foetuses have no testicles, no AMH is produced at this stage and the absence of AMH allows 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 significantly. In women, AMH will then steadily decline over their reproductive years, becoming very low and then undetectable after menopause.

AMH is important for a woman during her childbearing years. At birth, a female has about 1 million eggs (oocytes), which decrease in number during childhood to about 500,000. While many of these eggs do not mature due to natural degradation, a finite number of them are rescued by the follicle-stimulating hormone (FSH) to form mature follicles. AMH has a balancing effect on the cyclical actions of FSH during the monthly process of egg maturation and release (ovulation) as influenced by the presence of luteinising hormone (LH). 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. Determining the AMH level is 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 ovarian syndrome (PCOS). The excess follicles that occur in this syndrome produce abnormally large amounts of AMH, as also may be found in certain rare types of ovarian and testicular tumours.

As stated earlier, AMH also plays a vital part in sexual differentiation in the foetus. During the first few weeks of pregnancy, a 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 Mullerian ducts found in both male and female foetuses) 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 recognised as either male or female.

How is it used?

Anti-Mullerian hormone (AMH) is not a routinely ordered test but may be useful in specific circumstances.

AMH test in women:
Women of childbearing age may have an AMH test ordered along with other hormone tests, such as oestradiol and FSH, to estimate the remaining time left to conceive (ovarian reserve) while being evaluated for infertility. These tests are also useful in evaluating ovarian function and possibly in predicting the onset of menopause.

AMH may sometimes be ordered on a woman who will be undergoing assisted reproduction procedures such as in vitro fertilization (IVF); the concentration of AMH present is related to her likely responsiveness to treatment. A low level of AMH reflects poor ovarian response, indicating that a decreased number of eggs would be retrieved after ovarian stimulation. For this purpose, it is typically ordered along with other hormone tests and a transvaginal ultrasound (to count the number of follicles as a reflection of the woman's egg supply).

AMH can be elevated with polycystic ovarian syndrome (PCOS) due to the increased number of follicles and may be ordered to evaluate this condition.

Some ovarian cancers such as granulosa cell tumours, produce increased levels of AMH and/or inhibin B, which may be used as tumour markers to help evaluate response to treatment and monitor for recurrence.

AMH test in infants:

In an infant with genitals that are not clearly male or female (ambiguous genitalia), an AMH test may be ordered along with chromosome testing, hormone testing, and sometimes imaging scans to help determine the sex of the baby. In a male infant born with no visible testicles, low levels of AMH may account for the ambiguity of genitalia. If the testicles have not descended but are present in the abdomen, this test may be used to help determine whether they are functioning normally by measuring the AMH level.

When is it requested?

An AMH test may be ordered when evaluating ovarian function and fertility issues e.g. after chemo- or radiotherapy, especially when considering assisted reproduction procedures such as IVF, and when a doctor wants to determine a woman's likelihood of entering menopause.

AMH may be ordered when a woman has signs and symptoms of PCOS. Some of these include:

Abnormal uterine bleeding
Acanthosis nigricans
Acne
Absence of menstrual cycle (amenorrhoea) or irregular menstrual cycle
Decreased breast size
Enlarged ovaries
Hirsutism involving male hair growth patterns, such as hair on the face, sideburn area, chin, upper lip, lower abdominal midline, chest, areola, lower back, buttock, and inner thigh
Weight gain/obesity, with fat distribution in centre of the body
Skin tags in the armpits or neck
Thinning hair, with male pattern baldness

AMH may be ordered periodically on a woman with an AMH-producing ovarian cancer to monitor the effectiveness of treatment and to monitor for recurrence.

An AMH test may be ordered when an infant has ambiguous genitalia or when a male child's testicles have not descended properly.

What does the result mean?

Women
During a woman's childbearing years, a decreased level of AMH may indicate low ovarian reserve with diminishing fertility, resulting in minimal or less responsiveness to IVF treatment. It can also indicate premature ovarian failure.

An increased level of AMH is often seen with PCOS but is not diagnostic of this condition. Increased AMH may also indicate an increased or even excessive responsiveness to IVF and a need to tailor the procedure accordingly. A decreasing level and/or significant decline in AMH may signal the imminent onset of menopause.

Negative to low levels of AMH are normal in a female during infancy and after menopause.

When AMH is used as a tool to monitor an AMH-producing ovarian cancer, then a decrease in AMH indicates a response to treatment and an increase may indicate cancer recurrence.

Infants
In a male infant, absence or low levels of AMH may indicate a problem with the AMH gene that directs AMH production and may be seen with absent or dysfunctional testicles. Lack of male hormones may result in ambiguous genitalia and may cause abnormal internal reproductive structures. Normal levels of AMH and androgens in a male infant whose testicles have not descended indicate that they are present and functional but not physically located where they are supposed to be.

Is there anything else I should know?

Some in the medical community are advocating the use of AMH as a more routine test, for predicting the end of fertility and the onset of menopause, but there is not a consensus on this use. It is not considered a diagnostic or "stand-alone" test, but one that supports the diagnosis of one of the conditions mentioned.

Other female hormones fluctuate with a woman's monthly cycle; however, AMH is produced by growing follicles at a relatively steady rate. It is also not affected by oral contraceptives or pregnancy.

Common questions

Should every woman of child-bearing years have a AMH test?

For most women, the AMH test is not considered necessary unless they are having fertility issues. Most women will not need to have this test performed.