AMH is an interesting hormone that has been known about since the 1940s but is now only just coming into vogue as a predictor of female fertility. At birth, a baby girl may have around one or two million or more tiny follicles in her ovaries. Each of these will contain an egg. Some of these follicles containing an immature egg gradually disappear with age, so by the time she reaches puberty she will have somewhere between 100,000 to 500,000 eggs left. Thereafter eggs are constantly lost whether or not she ovulates regularly. By the age of 40, she is likely to have around 10% of her eggs remaining and this egg loss continues rapidly thereafter until the menopause. Follicles that are not lost gradually develop to what is called the pre-antral stage. The cells which line each of these follicles produce the hormone AMH, so measurements of AMH tend to give an indication of how many slowly maturing follicles remain in each ovary , the theory is, the more follicles the higher the level of AMH. Everyone ages at a different rates, so the loss of maturing follicles and therefore eggs varies from person to person. Consequently, AMH measurements are an indicator of how soon a woman is likely to run out of eggs.
It all sounds too good to be true. One problem is that a woman’s levels of AMH fluctuate from time to time. Another is the measurements of this hormone vary from lab to lab , the method for detecting this hormone is not ideal, and even the way the blood is stored before the test can make a difference to the result. Also, there is considerable variation from person to person. Nevertheless, AMH is a good indicator of how many eggs are likely to be collected during a single IVF treatment cycle. However, this is not always borne out by the likelihood of pregnancy. Some people with quite high results do not produce many eggs and others with low levels, may be relatively fertile. At present, although increasingly used, AMH measurements remain a bit controversial because it does not necessarily predict the chances of a pregnancy following IVF. Even women with quite low levels occasionally get pregnant. There are several other problems. High FSH levels are indicative of a lack of what is called ‘ovarian reserve’ i.e. reduced numbers of follicles. But very often the levels of FSH and AMH do not correlate well , that is to say that, for example, a woman can have high FSH levels but with normal AMH levels.
AMH can be measured at any time during the cycle. It is also used to predict, with modest success, the ovarian reserve after a cancer treatment, after surgery on the ovaries, and to predict the chances of hyperstimulation if gonadotropins are used to stimulate the ovaries. AMH is often raised in people with polycystic ovaries (PCOS). So it can be used to help this diagnosis in some women; but conversely, so it may be less good at predicting ovarian reserve in those with PCOS.
AMH levels are confusing. For one thing, they are usually measured in nanograms per litre but sometimes in picomoles which give a higher reading. A single measurement is usually quite inadequate to decide whether eggs are running out. And because AMH levels vary so much from the laboratory to laboratory or clinic to clinic, they are as yet not well standardised, it is important that you should enquire from your doctor what the normal levels are in the clinic you are attending and how much variability may be expected.
Despite countless breakthroughs in medical science, we still do not understand why some pregnancies will end in tragedy. For most of us, having a child of our own is the most fulfilling experience of our lives. All of us can imagine the desperation and sadness of parents who lose a baby, and the life-shattering impact that a disabled or seriously ill child has on a family.
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