TAC3 and Infertility: After the initial findings that loss-of-function mutations in TAC3 and TACR3 can lead to familial hypogonadotropic hypogonadism and infertility in human and that impairment of the TAC3/TACR3 system can postpone puberty in animal models, increasing evidence has been cumulated supporting the idea of GnRH and kisspeptin regulation by the TAC3/TACR3 system [33,34,35].