INVITED COMMENTARY Somatostatin infusion withdrawal and growth hormone release in dogs and man

The hypothalamic neuropeptides growth hormone-releasing hormone (GHRH) and somatostatin (SS), respectively, stimulate and inhibit the release of growth hormone (GH) from the anterior pituitary gland in both man and other animals. Even before the discovery of GHRH (in 1982) a series of small peptides, derived from met-enkephalin, had been developed and shown to specifically release GH in vitro (1). These GH-releasing peptides (GHRPs) along with a number of non-peptide analogues (collectively termed GH secretagogues; GHS) are now known to act on a specific GH secretagogue receptor (GHS-R), present in the hypothalamus and pituitary (2). Recently, a peptide isolated from rat stomach (and called ghrelin) was identified as an endogenous ligand for the GHS-R and suggests anothe