Activin is produced in the gonads, pituitary gland, placenta, and other organs: In the ovarian follicle, activin increases FSH binding and FSH-induced aromatization. It participates in androgen synthesis enhancing LH action in the ovary and testis. In the male, activin enhances spermatogenesis.

Is activin a hormone?

Activins were discovered in 1986 following the isolation of inhibins from porcine follicular fluid, and were characterized as ovarian hormones that stimulate follicle stimulating hormone (FSH) release by the pituitary gland.

What receptor does activin bind to?

Activin first binds to the type II receptors, which in turn recruit and phosphorylate type I receptors. The type I receptors then phosphorylate Smad2 and/or Smad3. The phosphorylated R-Smad forms a complex with Smad4 and is then translocated to the nucleus.