Somatostatin is a polypeptide hormone produced chiefly by the hypothalamus. It inhibits the secretion of various other hormones, such as somatotropin, glucagon, insulin, thyrotropin, and gastrin. Somatostatin is a hormone comprising two peptides, one built of 14 amino acids, the other of 28 amino acids. Somatostatin is secreted not only by cells of the hypothalamus but also by delta cells of stomach, intestine, and pancreas. It binds to somatostatin receptors. Somatostatin was first discovered in hypothalamic extracts and identified as a hormone that inhibited secretion of growth hormone. Subsequently, somatostatin was found to be secreted by a broad range of tissues, including those of the pancreas, intestinal tract, and regions of the central nervous system outside the hypothalamus.