Hypothalamic gonadotropin-releasing hormone (GnRH) is a decapeptide that stimulates pituitary synthesis and secretion of gonadotropins and, therefore, gonadal hormones. GnRH antagonists, of which thousands have been formulated, inhibit the hormone from binding to its receptor, inducing a pharmacological hypophysectomy. Peptide derivations of GnRH and non-peptide compounds are both in clinical trials or approved for assisted reproduction. As these compounds reach the market, the use of antagonists might expand to treatment of other hormonally dependent diseases, hormonal male contraception and growth inhibition of extra-pituitary cancer cells expressing GnRH receptors.