As regards the central impact of primary hypothyroidism, previous studies suggest that hypothyroidism can impact the hypothalamic–pituitary axis, causing hypogonadotropic hypogonadism through decrement of GnRH levels and lowering of gonadotropin production (Krassas et al., 2010; Toni et al., 2005). Here, GNRH1 is linked to hypogonadotropic hypogonadism.