FGFR1 and hypogonadotropic hypogonadism: Despite this strong genetic determinant, mutations in genes implicated in the regulation of hypothalamic–pituitary–gonadal axis have rarely been identified in cases of self-limited delayed puberty and often in relatives of patients with congenital hypogonadotropic hypogonadism (i.e., FGFR1 and GNRHR genes).