Growth hormone-releasing hormone: extrapituitary effects in physiology and pathology.

Growth Hormone-Releasing Hormone (GHRH) is secreted by the hypothalamus and regulates the release of growth hormone from the anterior pituitary gland. In addition to its endocrine role, this peptide has been shown to act as a growth factor in diverse malignancies. Recent studies indicate that GHRH is also a regulator of several important physiological processes. These processes which include the regulation of the metabolism of the reactive oxygen and nitrogen species are similarly enhanced by GHRH agonists. In contrast, GHRH antagonists can counteract the growth factor effects of GHRH. GHRH and its agonists have been shown to contribute to the recovery of heart tissue after myocardial infarction and can promote the survival and proliferation of pancreatic islets after transplantation into diabetic animals.