Hypogonadotropic hypogonadism.

Hypogonadotropic hypogonadism is characterized by failure of gonadal function secondary to deficient gonadotropin secretion, resulting from either a pituitary or hypothalamic defect, and is commonly seen in association with structural lesions or functional defects affecting this region. Although the genetic basis for idiopathic hypogonadotropic hypogonadism is largely unknown, mutations in several genes involved in the hypothalamo-pituitary-gonadal axis development and function have recently been implicated in the pathogenesis of this condition. Genes currently recognized to be involved include KAL-1 (associated with X-linked Kallmann Syndrome), gonadotropin-releasing hormone (GnRH) receptor, gonadotropins, pituitary transcription factors (HESX1, LHX3, and PROP-1), orphan nuclear receptors (DAX-1, associated with X-linked adrenal hypoplasia congenital, and SF-1), and three genes also associated with obesity (leptin, leptin receptor, and prohormone convertase 1 [ PC1]). Study of these mutations provides an important contribution in the understanding of the different stages of the reproductive axis development and physiology. Treatment options currently available for puberty induction, maintenance replacement therapy, and fertility induction are considered here. Gametogenesis can be induced with either exogenous gonadotropin or pulsatile GnRH therapy, depending on the etiology.