The biology of gonadotropin-releasing hormone and its analogs.

Gonadotropin-releasing hormone (GnRH) is one of the hormones involved in the complex hypothalamic-pituitary-gonadal axis which regulates the release of testosterone from the testes or estrogen from the ovaries. The development of GnRH analogs has helped elucidate the mechanism of action of the natural hormone, and provided possible new ways to treat hormonally related conditions including hormone-dependent cancers, precocious puberty, and endometriosis. The effectiveness of GnRH agonists in clinical use lies in their ability, with long-term administration, to suppress sex-hormone production. GnRH antagonists may eventually replace agonists because they are able to reduce hormone levels without the initial, temporary rise caused by agonists.