PCOS and Anti-Müllerian Hormone

Anti-Müllerian hormone (AMH), also known as Müllerian inhibiting substance, is a type of hormone secreted by an ovarian follicle as it matures. AMH levels are an important diagnostic measure as they are directly associated with the number of antral follicles found on the ovary each month.

Antral follicles, also referred to resting follicles, are those in the latter stage of development. Each has the potential to release an egg when fully mature.

Doctors may evaluate AMH levels for several reasons. Among them, the actual number of follicles—referred to as the ovarian reserve—can give doctors an idea as to how successful in vitro fertilization (IVF) may be. The higher the antral follicle count, the higher the AMH levels. The association has a high predictive value in this instance.

On the other hand, these very same measures can be a problem in women with polycystic ovary syndrome (PCOS). Women with PCOS will often have a high number of antral follicles and, as a result, an equally high level of AMH in their blood.

The problem with this is that too much AMH can actually stop ovulation from occurring. In a normal ovary, AMH works by preventing the premature development of a follicle and, in turn, the release of an immature egg during ovulation. When AMH levels are too high, they can inadvertently put on the brakes on this process, halting the maturation of an egg midstream.

In the same way that AMH can help predict the likelihood of a successful IVF procedure, it can help diagnose PCOS in women who may not have obvious signs of the syndrome.

AMH levels can be measured with a simple blood test. The blood can be drawn on any day of the menstrual cycle and, thereafter, sent to the lab for analysis. When returned, the results can tell us if the AMH is high, low, or normal.

A high level alone cannot diagnose PCOS since AMH levels typically decrease with age. As such, doctors will compare a woman’s age with the AMH results and use those to help make a diagnosis.

AMH can be extremely useful in diagnosing PCOS, especially in women over 35. Normally speaking, to confirm a PCOS diagnosis, a woman would need to meet two of three diagnostic criteria:

1. Delayed ovulation
2. Polycystic ovaries on an ultrasound exam
3. Lab results indicating an increase in certain hormones associated with PCOS symptoms (including hirsutism, acne, hair loss, etc.)

The problem with this is that polycystic ovaries on ultrasound are rare in women with PCOS after the age of 35. As such, if the other symptoms are vague, a PCO diagnosis may be missed or considered inconclusive.

By picking up an elevated AMH, doctors can sometimes support a diagnosis with reasonable confidence. While the test is not considered a substitute for a polycystic ovary ultrasound, it has diagnostic value in association with the other tests.

Moreover, in women known to have PCOS, elevated AMH levels correspond to an increased severity of symptoms, making its use all the more important in diagnosing and monitoring PCOS-related illnesses.