Origin of Mammalian Gonadotropin-Releasing Hormones

GONADOTROPIN-releasing hormone (GnRH) plays a pivotal role in reproduction. The existence of this neuropeptide, also called LHRH, was predicted in the 1950s (1), but the structure of the 10 amino acid peptide for porcine and ovine brains was not reported until the 1970s (2, 3). In the 20 yr since then, only one form of GnRH has been identified in most placental mammals, and this is still considered to be the sole neuropeptide causing the release of LH and FSH. The structure and functions of the mammalian form of GnRH have been reviewed a number of times (4s–8). Meanwhile, both mammalian GnRH and related forms of GnRH are now known to be present in primitive placental mammals, nonplacental mammals, and other vertebrates. Novel functions, in addition to the release of gonadotropins, exist. Studies of GnRH peptides and their genes have altered our views on the origin, function, and regulation of this neuropeptide.