GnRH analogues for contraception.

The production of chemical analogues of GnRH permits direct suppression of the pituitary-gonadal axis at the level of the gonadotroph. Continuous administration of GnRH agonists desensitizes the gonadotroph and ovulation is uniformly prevented, forming the practical basis for use in contraception. However, long-term treatment is constrained by variable effects on oestrogen secretion, which cause irregular bleeding patterns on the one hand and risks of hypo-oestrogenism on the other. Their use as a post-partum contraceptive has attractions because any analogue in milk should be without biological activity in the infant. GnRH antagonists have the advantage of immediate inhibitory action. They have potential application in circumstances in which agonists have been employed and, in addition, can interrupt any stage of the menstrual cycle. Clinical trials to utilise their potential antifertility action have not been performed. Use of GnRH analogues for contraception in women may require combination with low dose oestrogen and progestin and it has been proposed that such development may yield important benefits in health. When combined with testosterone, GnRH antagonists may form the basis for a male contraceptive.