Inhibin B

General Information

Inhibin is a 32 kDa glycoprotein hormone consisting of a heterodimer of two subunits, alpha and beta, linked by disulphide bonds. Inhibin-A and Inhibin-B have a common alpha-chain and different beta chains. Inhibin-A is secreted by the granulosa cells of the ovary and by the Sertoli or Leydig cells of the testes. Its function is to complete the regulatory loop in the control of follicle stimulating hormone (FSH) production by the anterior pituitary. During pregnancy, the major site of inhibin production is the placenta.

Whilst both inhibin-A and inhibin-B are present in all individuals, inhibin-B is the major circulating inhibin in the male.

The major clinical use is in monitoring of treatment of granulosa cell tumours of the ovary and the rare Sertoli cell tumours of the testes. Serum inhibin concentrations in patients with granulosa cell tumours are negatively correlated with the FSH concentrations, suggesting that the inhibin is intact and funcitonally active. The occasional reports of inhibin elevations in other ovarian carcinomas are not associated with FSH reductions, and probably relate to the secretion of biologically inactive fragments detected in some assays.