What is INHIBIN B ?

Formal Name: Inhibin A and Inhibin B, Tumor Marker, Serum

Inhibin A and inhibin B are hormones associated with reproduction and the development of oocytes (immature egg cells) in women’s ovaries. In women, these hormones are made mostly by the ovaries and by the placenta during pregnancy. Additionally, inhibin A and/or B may be produced by certain types of ovarian tumors. In general, tumors are uncontrolled growth of cells that may be benign (harmless) or cancerous. Inhibin A and inhibin B tests are two separate tests that measure the levels of these hormones in the blood.

Elevated levels of inhibin A and/or inhibin B may be present in the blood of a woman with a rare type of ovarian tumor called a granulosa cell tumor (the most common type of sex cord-stromal tumor). Blood levels of these hormones may also be elevated in some women with mucinous epithelial tumors. (For more details on these types of tumors, read the Ovarian Cancer article.) This makes inhibin A and B potentially useful as tumor markers. However, not all women with these ovarian tumors will have elevated inhibin A or B, so the tests may not be useful in all cases.

Most research on inhibin A and B as ovarian tumor markers have focused on postmenopausal women who normally have low to undetectable levels of these hormones. The use of these tumor markers in women of childbearing age (premenopausal) is less clear. Levels of inhibin A and B are usually higher in premenopausal women and the levels vary throughout their menstrual cycle. This can sometimes make it difficult to interpret results in premenopausal women.

How is the test used?

Inhibin A and/or inhibin B tests may be used along with a test for CA-125 to help determine whether you have an ovarian tumor. Testing may also be used to help diagnose a rare type of ovarian tumor called a granulosa cell tumor, and less commonly used to help diagnose a mucinous epithelial ovarian tumor.

If you are diagnosed with one of these types of ovarian tumors, blood tests to measure inhibin A and/or inhibin B may be used initially to determine whether your tumor is producing elevated levels of one or both of these hormones. If your inhibin A or B level is elevated prior to treatment, then the test may be used to monitor the effectiveness of treatment. The test may also be used after treatment to monitor for tumor recurrence.