Humans with ‘inactivating’ mutations in kisspeptin and/or its receptor show hypogonadotropic hypogonadism and delayed puberty (de Roux et al., 2003; Seminara et al., 2003), whist those with ‘activating’ mutations undergo precocious puberty (Teles et al., 2008; Silveira et al., 2010), suggesting that kisspeptin modulates GnRH pulsatility. Here, KISS1 is linked to hypogonadotropic hypogonadism.