Gonadotropin-releasing hormone (GnRH), also known as luteinizing hormone-releasing hormone (LHRH), regulates the reproductive hormonal cascade in vertebrates. Upon release from the hypothalamus, GnRH stimulates secretion of luteinizing hormone and follicle-stimulating hormone from the pituitary. In humans, the type I GnRH receptor is a GPCR that is unusual in the lack of a cytoplasmic C-terminal tail. Although some species contain a type II GnRH receptor, the human version of this second receptor appears to contain mutations that render it inactive. GnRH analogs (agonists) are used in low doses in a pulsatile fashion in the treatment of infertility, delayed puberty and cryptorchidism. GnRH agonists at high doses desensitize the receptor, and are used along with antagonists in the treatment of hormone-dependent diseases.