Kp and GPR54 are established regulators of the hypothalamic-pituitary-gonadal axis [2], [3] and loss-of-function mutations in GPR54 are associated with an absence of puberty and hypogonadotropic hypogonadism, a condition characterized by an absence of sexual maturation and low levels of gonadotropic hormones (LH and FSH), in humans. This evidence concerns the gene KISS1R and hypogonadotropic hypogonadism.