INHBB

INHBB is a gene that encodes the inhibin beta B subunit in humans. This protein is a subunit of both activin and inhibin, two closely related glycoproteins with opposing biological effects.

Function[edit | edit source]

The INHBB gene is a member of the transforming growth factor beta (TGF-beta) superfamily. The encoded protein is synthesized as a large precursor molecule that is cleaved to form a 12 kDa mature protein subunit and a 26 kDa N-terminal propeptide. This protein subunit can form homodimers or can be paired with the beta A subunit to form a heterodimer, both of which are active in inhibin and activin complexes.

The bioactive complex of inhibin B (alpha and beta B subunit) acts as a negative feedback regulator of follicle-stimulating hormone (FSH) secretion. On the other hand, the activin complex (beta B homodimer) stimulates FSH secretion. Therefore, the balance of inhibin B and activin secretion regulates FSH secretion and, consequently, reproductive function.

Clinical significance[edit | edit source]

Mutations in the INHBB gene are associated with premature ovarian failure and polycystic ovary syndrome. In addition, elevated levels of inhibin B are found in individuals with granulosa cell tumors and are used as a tumor marker in clinical tests.