The cyclic tetradecapeptide somatostatin is widely distributed throughout the body and is an important regulator of endocrine and nervous system function. It exerts its biologic actions by binding to specific high affinity receptors on the cell surface. Somatostatin inhibits the release of somatotropin. Somatostatin has also been shown in sympathetic nerves, mucosal cells, myenteric nerves of the gastrointestinal tract, salivary glands and in some parafollicular cells of the thyroid. Somatostatin positive cells may also be present in medullary thyroid carcinomas, C cell hyperplasia, thymic and lung tumors and pulmonary small cell carcinomas.
