What is being tested?
nhibin tests include separate tests for the two forms of inhibin - inhibin A and inhibin B, as well as a test that measures both forms together - total inhibin, often simply known as inhibin. Most testing is performed for women.
How is it used?
When is it requested?
Hormone levels such as inhibin B can be requested if a woman’s ovaries appear to be not be working well. This is usually because she is having trouble becoming pregnant or has symptoms and signs of polycystic ovarian syndrome, however this test has been superseded by anti-Mullerian Hormone (AMH).
In pregnant women having an inhibin A level to test for the wellbeing of the developing baby, the quadruple or quad test is performed in the second trimester of pregnancy - around the middle of pregnancy. It may also be recommended if earlier testing has been missed, if there have been problems with previous pregnancies or there is some other reason to be concerned about the growing baby.
In women who have a particular tumour of the ovary, or men with a testicular tumour, an inhibin level may be performed at the beginning of treatment to assess whether the tumour is producing inhibin. Throughout treatment, regular testing of the inhibin level may be used to monitor the effectiveness of treatment.
In men being tested because they are having difficulty becoming a father (infertility), levels of hormones such as inhibin B may be tested to see how well the testicles are working. Inhibin B is used to help assess the cause of conditions affecting the sex organs of babies (ambiguous genitalia).
What does the result mean?
In women having tests to see how well their ovaries are working, a low inhibin B level may suggest that the ovaries are not working well.
In pregnant women having a quadruple or quad test to check the wellbeing of the developing baby, a high level of inhibin A, along with other unusual test results, suggests the possibility of the baby having a serious abnormality. Further tests will be recommended to confirm whether there is a problem and, if so, assess what that problem is.
In women being treated for a particular tumour of the ovary, or men with a testicular tumour, the inhibin level should be low if the treatment is working well.
In males (baby boys or men) a low inhibin B level suggests that the testicles may not be working well.
Is there anything else I should know?
Inhibin tests may measure the level of all inhibin in the blood (total inhibin) or one of two different forms of inhibin - inhibin A or inhibin B. Your doctor will request the test that will be most useful for you.
If you are having regular inhibin levels to monitor your condition it is better if you have the same form of inhibin tested and if the test is performed in the same way every time. To be sure, your doctor may recommend that your blood sample is sent to the same laboratory every time.
In younger women, the inhibin level varies throughout the menstrual cycle. To understand what the test means, your doctor may need to know what stage of your cycle you are in at the time of the blood test.
No. Like most other `tumour marker' tests, the inhibin level on its own is not a reliable test of whether you have a tumour or not. It is most useful after you have been diagnosed with a tumour of the ovary by having tissue removed and examined under a microscope.
If your doctor has recommended an inhibin test, they may recommend other blood tests be performed at the same time. For example, if you are a woman having tests to see how well your ovaries are working, other tests may be requested including the anti-Mullerian hormone (AMH) level (also known as the `egg-timer’ test) and other female hormone levels such as follicle-stimulating hormone (FSH). If you are pregnant and having the quadruple or `quad' test, your blood will be tested for four hormones - inhibin A, alpha-fetoprotein, a form of the female hormone oestrogen (unconjugated oestriol) and a form of beta HCG (free beta HCG). If you are having inhibin testing as part of your treatment of a tumour of the ovary, other `tumour marker' tests may be performed, such as CA-125.
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