A 14-amino acid peptide named for its ability to inhibit pituitary GROWTH HORMONE release, also called somatotropin release-inhibiting factor. It is expressed in the central and peripheral nervous systems, the gut, and other organs. SRIF can also inhibit the release of THYROID-STIMULATING HORMONE; PROLACTIN; INSULIN; and GLUCAGON besides acting as a neurotransmitter and neuromodulator. In a number of species including humans, there is an additional form of somatostatin, SRIF-28 with a 14-amino acid extension at the N-terminal.

Any of several cyclic tetradecapeptides elaborated primarily by the median eminence of the hypothalamus and by the delta cells of the pancreatic islets; they inhibit release of a variety of hormones, including growth hormone, thyrotropin, corticotropin, insulin, glucagon, gastrin, secretin and renin.

Somatostatin is a polypeptide that is released in the gastrointestinal tract by delta cells and the hypothalamus. It functions as a key regulatory peptide that has many physiologic effects as an inhibitor for many other hormones, including gastrin, cholecystokinin, glucagon, growth hormone, insulin, secretin, pancreatic polypeptide,...