Mutations in gonadotropin-releasing hormone receptor gene cause hypogonadotropic hypogonadism

Idiopathic hypogonadotropic hypogonadism (IHH) is one of the most common causes of hereditary hypogonadism. Affected males and females present with irreversible pubertal delay, low serum levels of the gonadotropins follicle-stimulating hormone (FSH) and luteinizing hormone (LH), and sex steroids. The derangement appears to be deficient hypothalamic gonadotropin-releasing hormone (GNRH), as exogenous GNRH initiates pubertal development and fertility. IHH is genetically heterogeneous, but only mutations in two X-linked genes have been identified. KAL gene mutations in Kallmann syndrome produce IHH with anosmia, whereas AHC gene mutations result in adrenal hypoplasia congenita and IHH. X-linked recessive inheritance was once thought to be the most common cause of inherited IHH, but the frequency of KAL mutations is much less than anticipated.