Gonadotrophin-releasing hormone agonists for new approaches to contraception in man

Potent and long-acting stimulatory analogues to the hypothalamic gonadotrophin-releasing hormone (GnRH) were originally developed for profertility purposes. Paradoxically they proved to possess anti-fertility properties. Their anti-gonadal properties are at present being utilized for therapeutic purposes, e.g. contraception, treatment of central precocious puberty and sex steroid-dependent benign and malignant diseases of the reproductive organs, predominantly metastatic prostatic cancer. This review will be limited to the potential use of superactive GnRH agonists for contraception in women and men. Inhibit ion of ovulation by continuous GnRH agonist administration has been studied most extensively and will be dealt with in more detail. Other approaches to interfere with corpus luteum function (induction of in adequate luteal function, luteolysis or early abortion) have so far proved less successful. In males, complete azoospermia has not been consistently achieved by chronic high dose GnRH superagonist therapy alone. Testosterone supplementation is mandatory to avoid the unacceptable side effects associated with GnRH superagonist therapy, namely loss of libido and potency. Thus, to date, inhibition of ovulation by repeated intranasal GnRH agonist administration seems to have the greatest potential as a future contraceptive method. In long-term clinical trials, this new lead to birth control has already proved to provide safe, reliable and reversible contraception in women.