In the last decade much has been learned about the physiology and cellular biology of gonadotrophin-releasing hormone (GnRH). It is the first of the 'classical' hypothalamic releasing hormones to be widely used in clinical practice and, moreover, in diverse conditions. Its administration in a pulsatile, physiological manner is the most effective treatment for hypogonadotrophic anovulation (for revew see Clayton, 1987). However, greater application, from contraception to cancer therapy, has been achieved by continuous administration of long-acting agonist analogues, which rapidly induce gonadotroph desensitization (see below). While the principal target for GnRH action is the anterior pituitary gonadotroph, GnRH-binding sites and effects have been observed in other tissues. Although this review concentrates on the pituitary, I shall briefly discuss the extrapituitary actions of GnRH at the end.
At the outset it is important to recognize that GnRH has important actions on the gonadotroph in addition to releasing luteinizing hormone (LH). It is