**7. Kisspeptin in puberty**

In addition to its role in pregnancy and fertility, kisspeptin is also implicated in sexual development in humans. The target of the kisspeptin molecule is G-protein coupled receptor 54 (GPR54) [58]. A study by de Roux et al. demonstrated that humans with a defect in the *GPR54* gene exhibit isolated hypogonadotrophic hypogonadism, suggesting that kisspeptin is an important regulator of gonadal axis development [59]. This finding was then reproduced by an independent study by Seminara et al., who evaluated a large family with idiopathic hypogonadotrophic hypogonadism and generated *GPR54* knockout mice, which failed to undergo adult sexual development and had low serum gonadotropin levels [47]. In contrast, exogenous kisspeptin administration in prepubertal rodents and primates has been shown to induce precocious puberty [60]. Furthermore, Teles et al. describes a female with an activating mutation of *GPR54* who exhibited idiopathic central precocious puberty [61].

Kisspeptin is thought to be imperative in all phases of sexual development, beginning in the embryonic phase. During the second trimester of pregnancy, GnRH secretion first occurs and is required for normal testicular development [62]. Aberrant gonadal pathways can result in male infants born with microphallus or cryptorchidism [63]. Kisspeptin is suspected to be crucial in the stimulation of GnRH secretion in both infancy and puberty [62].
