Physiology, Gonadotropin-Releasing Hormone

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Gonadotropin-releasing hormone (GnRH), a decapeptide, is a part of the hypothalamic-pituitary-gonadal axis, and being a part of this system makes it vital for human reproduction. Since its discovery by a group of Nobel laureate Andrew V. Schally in 1971 from porcine hypothalamus as one of the earliest hypothalamic releasing hormones, it has been a center of attention of research scientists because of its central role in reproduction not only in humans but also in all vertebrates.

Over 20 different primary structures of GnRH and its receptors have been studied across different species. Compared to GnRH I, GnRH II is not widely distributed. It is found in the central nervous system, where it seems to act as a neuromodulator of sexual behavior and in the tissues of the female reproductive system, such as the endometrium, ovary, and placenta (and in tumors derived from these tissues). GnRH I & II are present in humans, GnRH-I (pGlu-His-Trp-Ser-Tyr-Gly-Leu-Arg-Pro-Gly·NH2) is mainly discussed in this review because it is the main isoform having the most physiologic importance in humans.

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