Growth Hormone-Releasing Hormone*

Abstract

THE PERIOD of time spanning the interval between the first postulate of the existence of a GH-releasing hormone (GRH) and the reports of its isolation and sequence encompassed more than two decades. In retrospect, several factors accounted for the exceedingly long interval. Most important were the requirement for development of new technology for both chemical purification and bioassay, the complexity of the stucture of GRH as compared to other releasing hormones, the susceptibility of GRH to biological inactivation during purification procedures, and the small quantities of hormone present in animal hypothalamus as compared with other hypophysiotropic hormones. However, once the sequence was identified, the rate of accumulation of knowledge concerning the biology of this hormone was extraordinarily rapid, resulting in information about the structure of its gene complex, the mechanisms of GRH action, the regulation of its secretion, and its potential use in treating both humans and animals. This review will address several of the above aspects of GRH, including the historical factors related to its isolation. We will also discuss extrapituitary actions of GRH, pathogenetic aspects of altered GRH secretion, and similarities and differences between GRH and other hypothalamic releasing hormones.