The Role of Inhibin B in Fertility Treatments

In addition to the traditional day three FSH and estradiol blood test, some fertility centers are using other tests, like the AMH (anti-mullerian hormone) and inhibin-B hormone test to evaluate a woman’s ovarian reserve, or how well her ovaries are working. These tests are usually performed as part of an infertility evaluation. 

Ovarian reserve testing is an important series of tests because the results can help direct the doctor to a treatment regimen. For example, a young woman with extremely poor ovarian reserve would likely be treated more aggressively than a young woman with normal reserve. These are often the first group of tests performed, before other, more specialized testing.

Not every center is using this test, and those that are aren’t using it for every patient. It is frequently used in cases where there is an unexpected poor response to the stimulatory medication, or in women who have unexplained infertility. Other centers use it for all of their egg donors, in order to optimize their donor pool.

Inhibin B is a hormone that is produced by certain cells in the ovarian follicles. When produced, it helps to suppress another hormone called FSH, or follicle stimulating hormone. FSH is secreted by the brain and causes an egg follicle to grow on the ovary.

As a woman ages, not only does the number of follicles on the ovaries decrease but so does the hormones produced by those follicles, like inhibin B. This makes it an effective test of a woman’s ovarian reserve or function.

The Inhibin B test is done through a simple blood draw, usually done on day three of your period. Your clinician will give you specific instructions, but generally, you will go into the office where they will draw your blood. Some offices are able to process the blood on-site, where others need to send it out to a specialized lab. Your results will be available a few days later. The doctor should call to discuss them with you.

The normal range depends on the specifications of the lab processing the specimen; however, a level above 45 pg/ml is considered normal. Levels below 45 pg/ml indicate declining ovarian function. Levels of Inhibin B can vary depending on where a woman is during her menstrual cycle. Levels can also be difficult to interpret in premenopausal women.

If the result is within the normal range, you have an excellent chance of getting pregnant. The doctor may suggest some basic monitoring or a less invasive treatment plan. If, however, the results are low or on the low end of normal, your chances of conception are significantly lower. Your doctor may recommend aggressive treatment or even the use of an egg donor to maximize your odds of pregnancy.

The cost of this test varies depending on the lab where the specimen is being processed. In addition, most insurance policies do not cover the cost of this test, so it is important to speak with your fertility center and the lab about potential expenses before you have the blood drawn. You don’t want to be surprised by an extremely high bill that you aren’t prepared for or can’t afford.