A clear and realistic guide to AMH and FSH

Often, when our doctors request tests to assess our fertility, we hear AMH and FSH mentioned. Both are measured to find out how our ovaries are working and to check how many eggs we have, also known as ovarian reserve. However, do we actually know what these hormones are for? Let's discover their importance in this article.

AMH

Anti-Müllerian hormone (AMH)is a hormone produced by the cells in your ovarian follicles. It is the most popular to measure ovarian reserve, as it is more reliable and does not vary during the cycle. We can estimate the number of eggs your ovaries have by measuring its level in your blood. This test should only be used for medical purposes, such as to predict how our body would respond to assisted reproductive treatments, like IVF or egg freezing. AMH should not be measured to check your ovarian reserve out of curiosity. This is because AMH levels are not helpful when predicting your success at conceiving naturally, as you can conceive naturally with low AMH. In short, you should not stress unnecessarily because your numbers are on the low side.

Variation of levels of AMH

AMH is produced by the cells of the ovarian follicles, and its level is very constant during the cycle with little variation month to month. There are some conditions where AMH can be very high. For example, women with Polycystic ovarian syndrome (PCOS), who have many follicles in the ovaries, usually have high AMH levels.

On the contrary, as we get older, our ovarian reserve decreases, therefore it is normal that AMH levels also decline with age. AMH levels can be also be affected by the use of contraceptive pills, resulting in lower levels than normal.

FSH

Follicle-stimulating hormone is one of the gonadotrophic hormones, which, along with the Luteinising hormone (LH), are released by the anterior pituitary gland in the brain. Its release depends on the Gonadotrophin-releasing hormone (GnRH), which travels from the Hypothalamus to the pituitary and stimulates the release of both FSH and LH at different stages of the menstrual cycle. FSH, as its name suggests, stimulates the selection and development of follicles in the ovary during the follicular phase. Therefore, without FSH, ovaries cannot produce a mature egg. For that reason, FSH level is used as one of the tests to measure ovarian reserve and function. FSH level varies during the cycle, so, it is preferable to measure it during your period, around day 2-4 of your cycle.

Abnormal levels of FSH

Having levels of FSH that are too high, or too low, might not be normal. Very high levels could mean our ovaries are not working properly and the feedback that the brain needs in order to release it has been lost. This condition is called hypergonadotrophic-hypogonadism and is associated with premature ovarian insufficiency when patients are running out of eggs. On the other hand, very low levels mean that there is not enough FSH to make your ovaries work and grow a follicle that can be released in ovulation. This leads to anovulatory infertility and is called hypogonadotrophic-hypogonadism, which can be caused by drugs, pituitary lesions, hyperprolactinemia, encephalic trauma, among others.

Your doctor will explain your results to you and prescribe treatment if it is needed.

Which test is better to measure ovarian reserve?

Both are useful. However, AMH is considered superior to FSH. It does not vary during the cycle or month to month, making it more accurate and able to detect changes in ovarian reserve earlier than FSH. Even though AMH is more reliable, FSH and Oestradiol (E2) are also important as they give us a better overall picture of our ovarian function.

Why is Oestradiol (E2) also important in assessing ovarian reserve?

It is important to analyse FSH levels along with E2. Remember the key role that E2 has in the menstrual cycle: it increases while the follicle is growing, stimulates ovulation and thickens the lining of the womb. That is why its levels, as well as FSH, should be measured early in the cycle, during the period. If we have low levels of FSH at the beginning of the cycle –which is normal –but we have not tested E2, we will not have the whole picture. We will not know whether those levels are normally low, showing a good ovarian function or reserve, or if levels being suppressed by high E2 levels, which is not normal. Therefore, it can cause difficulties and sometimes confusion if FSH is measured without E2measurements at the same time. In other words, FSH and E2 should be measured at the beginning of the cycle, and their results should be low at that stage.

What should we have learned about ovarian reserve tests by reading this?

• that AMH is superior to FSH to assess ovarian reserve
• that FSH should be measured along with E2 to get a better picture
• that AMH is useful to predict success in reproductive assisted treatments, but it does not predict the success of spontaneous pregnancy, so do not worry if your numbers are not what you expected.