KISS1 and hypogonadotropic hypogonadism: Inactivating mutations in genes encoding neurokinin B (NKB) or its receptor NK3R results in hypogonadotropic hypogonadism and failure to attain puberty in rodents and humans, a phenotype reminiscent of that of patients with mutations of Kiss1 or GPR54 (de Roux et al., 2003; Topaloglu et al., 2009).