Gonadotropin Releasing Hormone (GnRH) is down-regulated by hCG and believed to be an autocrine factor that regulates the ovary. The Gonadotropin Releasing Hormone Receptor (GnRHR) is synthesized in the pituitary gland. Activin A has been shown to stimulate the synthesis of GnRHR, illustrating a possible mechanism for the modulation of gonadotropin responsiveness to GnRH.