Activin/Inhibins

The activins and inhibins are among the 33 members of the TGF-β family and were first described as regulators of follicle-stimulating hormone (FSH) secretion and erythropoiesis. The activins were originally recognized for their abilities to augment the gonadotropin-releasing hormone (GnRH)-mediated release of FSH, and were named “activins” because their effects were functionally opposite to those of inhibin in this context. Inhibins and activins share common β subunits, with inhibins occurring as αβ heterodimers, whereas activins are ββ homodimers. Because inhibins were discovered and isolated before activins, the β monomers are designated inhibins βA and βB, and the genes are Inhba and Inhbb, respectively[1].