somatostatine

Somatostatine, also spelled somatostatin, is a peptide hormone that inhibits the secretion of a wide range of other hormones. It exists in two active forms, SST-14 and SST-28, derived from the precursor preprosomatostatin. Endogenously, it is produced mainly by D cells in the pancreatic islets and the gastrointestinal mucosa, and in the hypothalamus where it acts as a growth-hormone–inhibiting hormone.

Somatostatine exerts its effects by binding to somatostatin receptors (SSTR1-5) distributed throughout the body. Receptor activation suppresses adenylyl cyclase activity and reduces cAMP, inhibits voltage-gated calcium channels, and thereby decreases hormone secretion. It inhibits growth hormone and thyroid-stimulating hormone release from the pituitary and suppresses the secretion of many gut hormones, including gastrin, secretin, cholecystokinin, motilin, VIP, insulin, and glucagon. It also reduces pancreatic exocrine output and slows gastrointestinal motility.

In clinical practice, synthetic analogs with longer half-lives—such as octreotide, lanreotide, and pasireotide—mimic natural somatostatin and are used to treat conditions like acromegaly, neuroendocrine tumors, esophageal variceal bleeding, and other hormone-secreting tumors (for example VIPoma and carcinoid syndrome). Somatostatin receptor scintigraphy uses radiolabeled somatostatin analogs to image neuroendocrine tumors and related diseases.

Endogenous somatostatin has a short circulatory half-life, whereas its therapeutic analogs are formulated for longer action and various administration routes. Common adverse effects of long-term therapy include gastrointestinal discomfort, gallbladder problems such as gallstones, glucose intolerance or hypoglycemia, and bradycardia.