KISS1 and hypogonadotropic hypogonadism: The primary targets of kisspeptins are just the hypothalamic GnRH-secreting neurons (61) and, similarly to the deletion/mutation of GnRH or GnRH-R genes, target disruption of both kiss1 and GPR54 leads to hypogonadotropic hypogonadism and lack of sexual maturation (62, 63).