Anti-Mullerian Hormone (AMH) is currently the gold standard for ovarian reserve testing. To recap, AMH is produced by granulosa cells of early developing follicles, and correlates well with age and antral follicle count (AFC), where we covered in ‘3As of Fertility’. Here, we will explore what is normal level of AMH, and what it means if AMH is too high or low.
Whilst high AMH gives some assurance with regards to the number of eggs one has, it is however not an assurance of pregnancy. Even if it is low, it does not necessarily mean that you are infertile.Dr Lim Lei Jun, Fertility Specialist
Anti-Mullerian Hormone (AMH) is the most reliable marker to determine ovarian reserve. It is also the starter test ordered by fertility specialists. 20% of women will have either too high or too low AMH. Current social trends are clear, women are delaying childbearing into their 30s and in some closer to 40s. Knowing and tracking one’s AMH level can give a better understanding of one’s reproductive health, in addition to make choices about one’s reproductive goals and timeline. Whilst high AMH gives some assurance with regards to the number of eggs one has, it is however not an assurance of pregnancy. Even if it is low, it does not necessarily mean that you are infertile. It helps to understand that your reproductive years maybe shorter than you realized. This gets you to plan ahead about starting a family sooner or to consider egg freezing.
Recent years, several graphs for normal levels of AMH from birth to menopause have been developed. Collectively, the studies show that AMH is low during pre-pubertal development, rise during early puberty and plateau at 20- 25 years of age. After which, AMH gradually declines and it becomes undetectable around menopause.
It is not yet understood why AMH rise during childhood and adolescence. Hence, AMH can only be used to assess the extent of ovarian aging in women above 25 years of age.
When AMH exceeds 48pmo/L, it may indicate that the woman might be suffering from Polycystic Ovarian Syndrome (PCOS). Why is this important? PCOS is the most common hormonal disturbance affecting about 10% of reproductive-age women. It is also one of the commonest cause of subfertility. Due to hormonal imbalances, they are unable to produce a dominant follicle regularly which lead on to irregular and infrequent ovulation. This results in many underdeveloped and immature eggs. These eggs, within the follicles produce AMH. Hence, women with PCOS have an excess of AMH.
On the other hand, low AMH indicates lower number of eggs (follicles), often termed low ovarian reserve. It is important to read AMH in the context of many factors, most importantly your age. Women are said to have diminished ovarian reserve (DOR), when the number of eggs are much lower than expected for women the same age. When this happens, your doctor might get you to perform some genetic screening such as Fragile X Syndrome. Other causes of DOR are smoking, endometriosis, pelvic inflammatory disease, ovarian surgery, autoimmune diseases and cancer treatment. In many cases, no apparent cause can be identified. If a woman experience menopause before the age of 40, they have Premature Ovarian Insufficiency (POI), which impacts 1in 100 women. Women with POI can experience symptoms such as irregular periods, typically shortening of menstrual cycles well in their 30s.
How About the Quality of Eggs?
All these said, AMH does not tell us about the quality of eggs, which is important when it comes to getting pregnant. Fertility is directly related to egg quality, unfortunately there is no test for it. Age is the best predictor as quality declines in a predictable manner with age. The only way to test is to attempt fertilization of the eggs then perform test on the resulted embryos for chromosomal abnormalities. Women in their 20s have mostly (80%) normal eggs, although they too have abnormal ones. Whereas women in their 40s have mostly (80%) abnormal eggs, regardless of how healthy they have been.
To illustrate further, AMH of 7 pmol/L is low for 32 year old but it is within normal range for a 42 year old woman. They may yield similar number of eggs during IVF treatment, but 32 year old will have better chance of success with IVF as the proportion of normal eggs is higher with younger eggs. Our chances at pregnancy is significantly tied to the age of the eggs, which is the basis of the process.
This article is written by Dr Lim Lei Jun, Consultant OBGYN & Fertility Specialist, based in Sunfert International Fertility Center, Bangsar South.
Rotstein, A. (2020). Polycystic ovarian syndrome (PCOS) | McMaster Pathophysiology Review. Retrieved 26 August 2020, from http://www.pathophys.org/pcos/