FSH Level and what It Really Means

FSH is a hormone produced by the pituitary gland and is an indirect assessment of ovarian reserve. What this means is that indirectly it is related to assessing ovarian function, namely trying to assess the number of eggs remaining in the ovaries. In years past it was essentially the only way to assess ovarian function and ovarian reserve. Currently, however, it is well
understood that it is inadequate when used in and of itself. It can be very misleading and provide a “false sense of security” to patients and medical professionals. It remains of use. However, it should never be used alone in making a statement about ovarian function or reserve. It is clear with our data and others that it has a very high false negative rate when attempting to answer the question, “Do I have good ovarian reserve?”.

The bottom line is that in young patients (less than age thirty-five) the FSH
often is falsely normal, giving the impression that ovarian reserve is good. In my experience and observations over several hundred patients, in young atients with low ovarian reserve the FSH is often normal; and menstrual cycle irregularities are minimal.

Thus in assessing ovarian reserve, patients often get an FSH and rely upon menstrual history but are falsely led to believe that ovarian reserve is good when FSH and menstrual cyclicity are normal. We very often see normal FSH in these patients, but further assessment with simple blood tests and ultrasonography reveals low ovarian reserve. In patients over the age of thirty-five the FSH is a bit more reliable in indicating low ovarian reserve. That is to say when the FSH is high, ovarian reserve can reliably be diagnosed as being low.

However when the FSH is normal in patients over the age of thirty-five, this, as with patients under the age of thirty-five, does not necessarily mean that reserve is normal. In further explanation, ovarian reserve can be low in patients over the thirty-five even when the FSH is normal. So, again in and of itself the FSH is a poor indicator of ovarian reserve in patients over the age of thirty-five and an even worse indicator in patients under the age of thirty-five. Therefore, simple further tests need to be done to put the test results into proper context for any individual case.

When the FSH is elevated (over 9) in any age group of patient, the ovarian reserve is often low. his is why at SIRM it is routine for us obtain the following tests in addition to FSH to give us the best picture of ovarian reserve thus allowing us to put it into context with the individual couple: FSH, inhibin B, AMH, and antral follicle count (AFC). If one were to ask me which of these tests if the best, AFC is by far the most useful clinically in managing patients with fertility issues, regardless of what those issues might be (endometriosis, tubal factor, male factor, etc.).

Ovarian reserve remains the single most important factor in reproductive success; not to say that other issues are not important obviously, but this is always the most important part of the evaluation. This part of the evaluation with blood tests and ultrasonography can be done in a single visit early in the menstrual cycle, easy to organize. Information is obtained immediately with the follicle count assessment and can be discussed on the spot with respect to the patient’s and couple’s issues.

So, the take-home point above anything else from this information is that one should not rely on the FSH number alone, because even if it is normal, there can still be significant low ovarian reserve, and simple further assessment is necessary to give one the full picture. High FSH is a reliable indicator of poor ovarian reserve in most cases, but further assessment is still necessary to understand the degree of low reserve.