Somatostatin

Somatostatin is an endogenous peptide hormone indicated for treating acute bleeding from esophageal varices, gastrointestinal ulcers and gastritis; preventing postoperative pancreatic complications; and inhibiting secretions of the upper gastrointestinal tract, pancreas and biliary tract.

Also referred to as growth hormone-inhibiting hormone, somatostatin is a naturally occurring peptide hormone existing in 14 or 28 amino acid residue forms that modulates the endocrine system. Secreted by pancreatic islet D cells, it suppresses the release of insulin and glucagon; it is also produced in the hypothalamus, where it inhibits the anterior pituitary’s secretion of growth hormone and thyroid-stimulating hormone. Somatostatin is initially synthesized as preprosomatostatin, a 116 amino acid precursor, which undergoes endoproteolytic cleavage to form prosomatostatin. Prosomatostatin is further processed into two bioactive isoforms: somatostatin-14 (SST-14) and somatostatin-28 (SST-28), the latter being an N-terminally extended variant of SST-14. The biological effects of somatostatin are mediated through the signaling pathways of G protein-coupled somatostatin receptors.

The antineoplastic properties and potential clinical applications of somatostatin in various malignancies have been extensively studied, including pituitary adenomas, gastroenteropancreatic neuroendocrine tumors (GEP-NETs), paragangliomas, carcinoid tumors, breast cancer, malignant lymphoma and small-cell lung cancer. Clinically, somatostatin is used in the diagnosis of acromegaly and gastrointestinal tract tumors. To optimize pharmacokinetic properties for effective management of acute conditions such as esophageal varices, synthetic somatostatin analogues have been developed. Octreotide, a long-acting somatostatin analogue that inhibits the secretion of multiple hormones, is clinically used to alleviate symptoms of rare gastroenteropancreatic endocrine tumors and treat acromegaly.