Inhibin-B

Function

Inhibin-B is a peptide hormone produced by the granulosa cells in the ovaries of women and the Sertoli cells in the testes of men. Its primary biological function is to provide negative feedback to the pituitary gland to inhibit the secretion of Follicle-Stimulating Hormone (FSH). By regulating FSH, Inhibin-B plays a pivotal role in the control of gametogenesis—the production of eggs in women and sperm in men.

Why it is Ordered

This test is a cornerstone of reproductive health assessments. In women, it is primarily ordered to evaluate ovarian reserve, which reflects the quantity and quality of remaining eggs. It is often measured on day 3 of the menstrual cycle alongside FSH and Anti-Müllerian Hormone (AMH). In men, it is used to assess spermatogenesis and testicular function, particularly in cases of unexplained infertility or to evaluate the success of a testicular biopsy. Additionally, it serves as a tumor marker for certain types of ovarian cancers, specifically granulosa cell tumors.

Associated Conditions

• Ovarian Insufficiency: Low levels in women suggest a declining egg count, often associated with perimenopause or Premature Ovarian Failure (POF).
• Male Infertility: Reduced levels in men correlate with impaired sperm production and Sertoli cell dysfunction.
• Ovarian Neoplasms: Abnormally high levels can indicate the presence of specific germ-cell or sex cord-stromal tumors.
• Assisted Reproduction: Used to predict the response to ovulation induction in IVF protocols.