In humans, the role of KNDy system has been clarified by the association of loss-of-function mutations in the kisspeptin (KISS1), kisspeptin receptor (KISS1R), neurokinin B (TAC3), or neurokinin B receptor (TACR3) genes and delayed puberty and hypogonadism (17–19). Here, TACR3 is linked to hypogonadism.