[Hypothalamic factors: current findings]

The last few years have seen the isolation, characterization and synthesis of two new hypothalamic peptides, the growth-hormone releasing factor (GRF) and the corticotrophin-releasing factor (CRF). GRF selectively stimulates pituitary growth hormone. It is interesting to note that GRF was isolated from two pancreatic tumors which were responsible for an acromegalic condition in the two patients. Hypothalamic GRF (1-44) has been found to be identical to this pancreatic GRF. CRF was isolated first from ovine hypothalamus and later characterized in several species and in the human. CRF specifically stimulates the secretion of ACTH and of beta-endorphins, and other fragments of the common precursor named pro-opiomelanocortin. Chemical synthesis of analogues of hypothalamic peptides, and in particular of GnRH (gonadotrophin-releasing hormone), has made available new molecules which form agonists as well as antagonists. After a short period of gonadotrophin stimulation GnRH agonists induce desensitization of the pituitary and a decrease in secretion of the gonadotrophins and the sex steroids by the gonads. Their usefulness is presently being tested in several conditions such as prostate cancer, endometriosis, breast cancer and idiopathic precocious puberty, and as a contraceptive method. On the other hand, pulsatile administration of GnRH restores deficient reproductive functions in certain conditions such as anovulation or azoospermia.