Inhibin A and Inhibin B tests

Inhibin test measures the protein based hormone inhibin level in the blood. Inhibin is used for ovarian cancer diagnosis and sometimes “inhibin A” test is added to the triple test to increase the sensitivity of the test for down syndrome screening. There are 2 kinds of inhibin in blood circulation as “inhibin A” and “inhihin B” and they are detected by the laboratory tests that have same names with the hormones.

How the inhibin A and inhibin B tests are done?ovarian cancer inhibin b

A tube of blood is needed for inhibin test so you need to give a blood sample usually from a vein on your arm inside of your elbow or on the back of your hand. Blood collection is an easy and short procedure for you and you don’t need to worry about. You may feel pain only for a few seconds during the process. All blood collection takes 1-2 minutes at most.

Inhibin production in the body

Inhibin A and inhibin B  are produced in ovary in women and in men inhibin B is produced in testis. Inhibins are protein formed hormones. In women inhibin is produced by the developed egg and corpus luteum also by placenta during the pregnancy. Inhibin B is produced by developing follicles.

Purpose of inhibin A and B tests

Inhibin A test usage

  • Inhibin A  test is used as  a component of quadruple test for down syndrome( trisomy 21) screening and also screening of trisomy 18, turner syndrome, neural tube defect and other aneuploidies
  • Early determination of pregnancy in IVF (in vitro fertilization); inhibin A is more reliable than HCG test because of the external HCG usage
  • Inhibin A and inhibin B tests (total inhibin) are used to diagnose and monitor the treatment of some kinds of ovarian cancers, they are used with the CA 125 test to diagnose the 95% of ovarian cancersdown syndrome inhibin a

Inhibin B test usage

  • Inhibin B is used to evaluate the ovarian reserve to understand fertility status
  • Monitoring pubertal transition in girls
  • Monitoring the menopausal transition; predicting the menopause by inhibin B test
  • Measuring the ovarian reserve before IVF treatment
  • Diagnosis of ovarian cancer
  • Monitoring the puberty status and gonadal function in men
  • Diagnosis of infertility in men; low inhibin B level is a sign of insufficient sperm cell production in testis
  • Monitoring testis tissue with “inhibin B” instead of testis biopsy

Functions of inhibins

Main function of inhibin is to inhibit the FSH hormone secretion by pituitary

How inhibin levels change?

Inhibin A and B levels change normally in menstruation period

Inhibin A and B levels are very low after menopause by depletion of follicles


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