This test is used to evaluate female fertility (and more rarely, male fertility) or for the diagnosis and monitoring of certain types of ovarian tumours. Inhibin B and Inhibin A are two protein hormones produced by ovary cells in females and testicular cells in males. They suppress the secretion of follicle-stimulating hormone (FSH), a hormone involved in the menstrual cycle and sperm production.
Inhibin B levels on the third day of the menstrual cycle provide an indication of the ovarian reserve (potential number of egg cells that can be fertilized), a very useful piece of information for fertility clinics. Inhibin B levels can also be very high in certain sub-types of ovarian tumours (granulosa cell tumours, mucinous tumours). This test complements the information provided by the CA 125 test, another marker of ovarian tumours. Fluctuations in Inhibin B levels during the menstrual cycle can complicate the interpretation of results in premenopausal women.