Kisspeptin is a neuropeptide hormone that plays an important role in the hypothalamus, stimulating the release of gonadotropin-releasing hormone (GnRH). GnRH travels along the hypophyseal portal system and connects with its receptor site at the anterior pituitary gland where it stimulates the secretion of luteinizing hormone (LH) and follicle-stimulating hormone (FSH). LH and FSH in turn stimulate spermatogenesis in men and ovarian production of sex steroids in women. Kisspeptin testosterone is a natural alternative to human chorionic gonadotropin (HCG). HCG has been banned from compounding pharmacies in Florida and across the US, so kisspeptin is poised to fill this niche by providing a normal hormonal feedback loop.
The direct testicular effects of kisspeptin have been studied in various species and range from acceleration of germ cell progression in amphibians to alteration of oestradiol signaling in mammals. Moreover, kisspeptin is expressed in the seminiferous tubules of adult mice and has been shown to interact with Leydig cells, which play a key role in testicular steroidogenesis.
However, the direct effect of kisspeptin on spermatogenesis and sex steroids remains to be determined. Some researchers suggest that the boost in circulating LH and testosterone produced by kisspeptin may simply be due to a direct increase in sperm count, rather than altering the natural production of these hormones, which is usually controlled by a normal feedback system. Other studies have indicated that chronic peptide infusion increases the level of sperm motility in animals, and the apoptosis of ovarian and testicular cells, which is associated with the degeneration of the corpus luteum in postmenopausal women.