Kisspeptin Hormone: Revolution in Reproductive System Physiology

The control of reproduction has been attributed to the actions and feedforward of the sex steroids gonadotropin-releasing hormone (GnRH), luteinizing hormone (LH), and follicle-stimulating hormone (FSH). However, recent findings, including the identification of kisspeptin neurons and a kisspeptin-GnRH-LH/FSH axis, have prompted a reevaluation of reproductive regulation. At first, the KISS1 gene encoding kisspeptin was thought to belong to a group of genes called metastasis suppressors. Vertebrate and mammalian genomes have been enriched with Kiss and KissR gene variations during the last two decades. In 2003, kisspeptins and their receptor, KISS1R, and their role in the neuroendocrine-reproductive axis were discovered. This finding radically altered our understanding of reproductive physiology. These discoveries support the role of kisspeptins and their receptor as gatekeepers of sexual maturity at the outset of puberty and as key processors in the adult-life dynamic control of the gonadotropic axis. The significance of kisspeptin signaling in spermatogenesis and sperm quality is still debatable, even though Kiss1 and Kiss1R are expressed peripherally in the testes. Numerous processes, including steroidogenesis, follicular maturation, ovulation, and ovarian senescence, are affected by kisspeptin activity. Therefore, kisspeptin analogs (both agonists and antagonists) may be useful as therapies for those with disorders affecting the reproductive system. This overview focuses on the evolution, localization, and reproductive importance of the Kiss–KissR pair.