Anti-Mullerian Hormone (AMH)
The Anti-Mullerian hormone (AMH) is formed by the eggs in your ovaries. The AMH level is the best hormone marker to determine your ovarian reserve. The ovarian reserve and your age largely determine how long you have to get pregnant and when menopause begins.
In each of your two ovaries are many thousands of eggs at different stages of maturity. As soon as these eggs are 1–5 mm in size (they are called secondary follicles at this stage), they begin to produce the anti-Mullerian hormone. More specifically, this process happens in the granulosa cells that surround the oocyte.
Fig. 1: The granulosa cells of maturing oocytes produce AMH. The more eggs in your ovaries, the greater your AMH value, and the larger your egg stock. The fewer eggs in your ovaries, the smaller your AMH value, and the closer you are to the menopausal transition and menopause.
What Affects Your AMH Level?
When interpreting your AMH value, it is important to consider the test method used (different assays have different ranges and cut-off levels), your age, and your lifestyle. Smoking and an increased body mass index, for example, often lead to a reduced AMH level. Also, taking the pill or using other hormonal contraceptives will change your AMH levels.
There are also other markers for determining the oocyte reserve: the follicle-stimulating hormone (FSH), the number of visible follicles in ultrasound (antral follicle count; AFC), and the inhibin-B hormone. However, none of these markers is as reliable for interpreting the ovarian reserve as AMH, as numerous studies show. For example, FSH values fluctuate so much that the FSH would have to be measured at least three times in order to make an assessment.
AMH can be used to estimate how long women are still fertile. Within a certain range, AMH can even be used to predict the onset of menopause (defined as a year of absent menstrual bleeding). Plus, AMH is also beneficial for in vitro fertilization (IVF): With the help of the AMH value, the number of eggs that can be obtained by the hormonal stimulation of the ovary can be predicted.
What Does a Low AMH Level Mean?
AMH levels below a certain threshold mean that your ovarian reserve is diminished. Depending on the AMH assay used, this threshold could be 1.0 ng/ml or 0.5 ng/ml. Levels below 0.1 ng/ml mean that your ovarian reserve is most likely exhausted.
A diminished ovarian reserve, especially if you are older than 37, will likely make it more difficult to get pregnant.
Important: Your AMH level must be interpreted according to the test method used and your age. An AMH of 1.2 ng/ml means something different for a 28-year-old than for a 40-year-old. Some AMH assays use pmol/l instead of ng/ml – if your test result shows pmol/l, then higher thresholds for diminished and exhausted ovarian reserve apply. If you use hormonal contraception, your AMH value is reduced as a result—this too must be taken into account when interpreting your result.
What Does a High AMH Level Mean?
A high AMH value either means that you have a large egg supply or that you may have polycystic ovary syndrome (PCOS).
Again, it is important to interpret the AMH value in combination with your age. For example, a value of 4.2 ng/ml is normal for a woman in her mid-20s but not for a woman in her late 30s. Excessively high AMH values are almost always connected to PCOS.
Precautionary egg freezing, also known as “social freezing,” is establishing itself in a growing number of countries as a method of preserving fertility. Whether or not the egg reserve is sufficient enough to gain eggs for social freezing as part of hormone stimulation can be determined with AMH.