Low AMH – effect on fertility

What is the AMH hormone?

Anti-Mullerian hormone (AMH) is a substance produced by the small (2 – 8mm) preantral and antral follicles in the ovary and can be measured by a blood test to get an idea about the woman’s ovarian reserve. Other tests available for ovarian reserve are blood tests for FSH (Follicle Stimulating Hormone) (done between day 2-5 of the menstrual cycle), inhibin B and Ultrasound scan for antral follicle (defined as small follicles between 2-8mm) count. AMH can be measured at any time during the menstrual cycle and both AMH and antral follicle count have good predictive value for response to ovarian stimulation during IVF.

AMH is a blood test to measure ovarian reserve and can be performed at any time of the menstrual cycle.

What is the cause of low AMH?

Unlike men, when sperm production can last almost indefinitely, in women the numbers of eggs in the ovary are determined at birth. It depletes with age and when the remaining follicles are too few to respond to hormonal signals, menopause ensues. At birth, the follicles are very immature (primordial follicles) with a very immature egg. From puberty, every month, few follicles move on to different phases (preantral, antral follicles) and one becomes dominant follicle (which ovulates) and others are destroyed by nature (atretic follicles).

Throughout a woman’s life out of 400,000 follicles at birth, only around 400 ovulates. Since a large number of follicles are destroyed by nature every month, the egg reserve diminishes with age.

Since the preantral and antral follicles produce AMH, its level diminishes with the decline in the number of follicles with age. The rate of this decline varies between individuals and is determined to a large extent by the genetic makeup of the individual and also individual lifestyle factors, such as smoking.

Women are born with a set number of eggs, which they lose throughout their reproductive life. The rate of decline in ovarian reserve is largely determined by genetic make up and lifestyle factors eg. smoking.

Can you improve your AMH level?

There are no natural/medicated ways to increase the level of AMH. Even in women on oral contraceptive pills, who are not ovulating, the natural decline in ovarian reserve continues.

AMH levels by age chart

AMH levels vary according to the assays used by the laboratory to analyse the result.

Reference Ranges (Healthy women, pmol/L)

Age range (2.5th percentile - 97.5th percentile)

20 – 24 years - (8.7 - 83.6)

25 – 29 years - (6.4 - 70.3)

30 – 34 years - (4.1 - 58.0)

35 – 39 years - (1.1 - 53.5)

40 – 44 years - (0.2 - 39.1)

45 – 50 years - (0.1 - 19.3)

According to Roche Elecsys AMH Plus assay

What does it mean to have low AMH?

Low AMH in itself in a regularly ovulating woman is not a cause for the delay in conception. While these tests predict the response to ovarian stimulation during IVF, they are quite limited in their accuracy to predict chances of spontaneous conception. The most important factor for spontaneous conception is whether the woman is ovulating. If the woman has a very regular cycle between 26 – 32 days, it is more than likely she is ovulating.

Ovarian reserve tests, especially AMH do not predict egg quality, which is largely determined by the age of the woman. Hence, the chance of conception in young women with low AMH but regular menstrual cycle remains good. Thus the value of these tests in predicting natural fertility is very limited.

These tests are however useful prior to IVF treatment, as they can be used to anticipate the response to ovarian stimulation and hence decide the optimal mode of ovarian stimulation during IVF.

AMH <5.4 pmol/L is considered to indicate a low response during IVF and a level >25 pmol/L is considered to indicate a high response, according to NICE guideline.

Low AMH in itself is NOT a cause for infertility, so long periods remain regular.

Does low AMH means menopause is imminent?

Low AMH indicates depleting pool of antral follicles and hence it can indicate the timing of menopause. Women with low AMH is likely to attain menopause earlier.

However, the age of menopause depends on various factors like ethnicity, genetic makeup, smoking, chemotherapy, ovarian surgery and age of the first period. Hence it is not possible to predict the exact age of menopause from AMH alone.

Very low AMH might indicate earlier menopause, but exact timing is not possible.

According to the American College of Obstetricians and Gynaecologists, it is reasonable to encourage a woman to attempt to conceive sooner rather than later if her ovarian reserve is found to be diminished, as her window of opportunity to conceive might be shorter than anticipated.

Written by Dr Anupa Nandi