Growth hormone (GH) secretagoguesand neuroendocrine regulation of GH secretion

Abstract

In 1984, Bowers et a12 described the first member of a class of synthetic growth hormone (GH) secretagogues, GH-releasing peptide-6 (GHRP-6), and showed that this compound stimulated GH secretion by a direct action on the pituitary gland. Only now, over 15 years later, are we beginning to build a detailed picture of the complexity and diversity of the actions of these compounds. The first direct evidence that these compounds are also centrally active was provided by Dickson et al., 2,3 and subsequent studies by this research group have investigated the hypothalamic circuits through which these secretagogues operate. The GH secretagogue receptor was cloned in 1996 and shown to be present in the pituitary gland and hypothalamus. 4 It soon became evident, however, that the GH secretagogue receptor is also located in other regions of the central nervous system and even in peripheral tissues. 5 This review will largely focus on the effects of GH secretagogues on the neuroendocrine hypothalamus.