Inhibin is a protein that down regulates FSH synthesis and inhibits FSH secretion.
Inhibin and a number of other structurally related proteins such as activin, anti-Müllerian hormone, bone morphogenetic protein, and growth differentiation factor belong to the TGF-β protein superfamily.
In both females and males, inhibin inhibits FSH production and GnRH release from the hypothalamus. However, the overall mechanism differs between the genders:
Inhibin is produced in the gonads, pituitary gland, placenta and other organs.
In women, FSH stimulates the secretion of inhibin from the granulosa cells of the ovarian follicles in the ovaries. In turn, inhibin suppresses FSH.
· Inhibin B reaches a peak in the early- to mid-follicular phase, and a second peak at ovulation.
· Inhibin A reaches its peak in the mid-luteal phase.
Inhibin secretion is diminished by GnRH, and enhanced by insulin-like growth factor-1 (IGF-1).
In men, it is a hormone that inhibits FSH by negative feedback. It is secreted from the Sertoli cells. Androgens stimulate inhibin production; this peptide may also help to locally regulate spermatogenesis.
Inhibin has been used as a marker for ovarian cancer.
Inhibin B may be used as a marker of spermatogenesis function and male infertility. The mean serum inhibin B level is significantly higher among fertile men (approximately 140 pg/ml) than in infertile men (approximately 80 pg/ml).
Now in Saridar Lab, Inhibin level is available and routinely done.