Inhibin A and Inhibin B Tumor Markers
- Formal Name:
- Inhibin A and Inhibin B
- Tumor Marker
At a Glance
Why Get Tested?
To help determine whether you have an ovarian tumor, often along with a test for CA-125; to help diagnose rare ovarian granulosa cell tumors and sometimes mucinous epithelial ovarian tumors, to evaluate the effectiveness of their treatment and to monitor whether the tumor has returned after treatment
When To Get Tested?
When it is suspected that you have an ovarian tumor (e.g., you have a mass in the pelvic area); after you have been diagnosed with a granulosa cell tumor or mucinous epithelial tumor and before starting therapy; at intervals during and after treatment
A blood sample drawn from a vein
Test Preparation Needed?
What is being tested?
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 an 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. 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.
When is it ordered?
Inhibin A and B tests may be ordered when you have a mass in your pelvis, and it is suspected that you may have an ovarian tumor.
These tests may be ordered after you are diagnosed with an ovarian granulosa cell tumor or sometimes a mucinous epithelial ovarian tumor and before you begin treatment. If levels are elevated, then the test(s) may be ordered on a regular basis throughout your treatment and periodically after you have completed treatment to monitor for tumor recurrence.
What does the test result mean?
Results of inhibin A and inhibin B tumor marker tests are interpreted in the context of your medical history in addition to results of other tests, such as CA-125.
If you have a pelvic mass, an elevated inhibin A, inhibin B and/or CA-125 is a concern but does not necessarily indicate that you have an ovarian tumor. This finding would prompt further laboratory testing and medical evaluation. It is not usually possible to tell whether an ovarian tumor is cancerous until the tumor has been sampled and tested. A pathologist uses a microscope to examine the sample and determine whether cancerous cells are present.
If you have been diagnosed with and are being treated for a granulosa cell tumor or mucinous epithelial tumor, results may mean one of the following:
- If your inhibin A and/or B levels are initially high and then fall during therapy, this generally indicates that the tumor is responding to treatment.
- If the inhibin A or B levels rise or stay the same, then your tumor may not be responding to therapy.
- An initial fall in inhibin levels after treatment is completed, with a subsequent rise in inhibin levels may indicate that your tumor is returning.
If you have an ovarian tumor and are premenopausal, then interpreting results can sometimes be challenging. This is because both inhibin A and B levels normally rise and fall throughout your menstrual cycle.
Can I have an inhibin test to screen for ovarian tumors or ovarian cancer?
No. Like most other tumor marker tests, the inhibin level on its own is not a reliable test of whether you have an ovarian tumor or cancer or not. It is most useful after you have already been diagnosed with a tumor or cancer of the ovary by having tissue removed and examined by a pathologist using a microscope.
Besides ovarian tumors, is inhibin testing used for other conditions?
Yes. Inhibin testing may be used for other conditions:
- Inhibin B testing may be used as part of an infertility evaluation. (Inhibin B in Infertility)
- Inhibin A testing is used as part of the screening process for Down syndrome during pregnancy (Maternal Serum Screening, Second Trimester (Quad Screen))
How long does it take for results?
Inhibin A and B testing is not offered by all laboratories. Your blood sample may be sent to a reference laboratory and it may take several days for results.
How are ovarian tumors treated?
Treatment usually depends on the type of tumor and whether it is cancerous or not. The main treatment is surgery to remove the tumor and may also include chemotherapy, hormone therapy, targeted therapy, and/or radiation therapy.
Bronwyn H. Bryant, MD, Associate Program Director, Pathology Residency Program Assistant Professor, Pathology and Laboratory Medicine, University of Vermont Medical Center.
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