Somatostatin

Somatostatin (SRIF, Somatotropin Release-Inhibiting Factor) is a regulatory peptide discovered in 1972 by Brazeau and Guillemin as a potent inhibitor of growth hormone secretion. It exists in two coexisting bioactive forms: SST-14 (14 amino acids) and SST-28 (28 amino acids), derived from the same preprosomatostatin precursor by differential proteolytic cleavage.

Physiologically, somatostatin is a universal inhibitor of hormonal and exocrine secretions. Produced in the hypothalamus, endocrine pancreas (δ cells of islets), digestive tract and central nervous system, it inhibits the secretion of growth hormone, TSH, insulin, glucagon, gastrin, secretin, cholecystokinin, and numerous other peptide hormones. It also exerts an antiproliferative effect on tumor cells expressing its receptors, a property exploited in endocrine oncology.

Somatostatin acts via five G-protein coupled receptor subtypes (SSTR1 to SSTR5), all inhibitory through Gi/o and decreased intracellular cAMP. Their differential tissue distribution explains specific effects: SSTR2 dominates in the pituitary and neuroendocrine tumors, SSTR5 is important for GH and insulin inhibition, SSTR1/3/4 are more widely distributed. This receptor heterogeneity stimulated the development of selective analogues to precisely target certain biological actions.

Therapeutic analogues of somatostatin constitute a mature pharmaceutical class. Octreotide, a cyclic octapeptide introduced in 1988, preferentially targets SSTR2 and SSTR5, with extended half-life (≈90 min versus 2 min for native somatostatin) enabling spaced administrations. Lanreotide and pasireotide represent evolutions with varying selectivity profiles and durations of action. Sustained-release formulations (octreotide LAR, lanreotide Autogel) ensure monthly coverage.

In exploratory research, somatostatin and its analogues enable study of several domains: fine hormonal regulation of the somatotropic axis, SSTR receptor signaling and their desensitization/internalization mechanisms, effects on cell proliferation in experimental oncology, and interactions with other neuroendocrine pathways (ghrelin, GHRH). On lab-peptides-france.com, native somatostatin may be available on request for research use. Laboratories working on the hypothalamic-pituitary axis or neuroendocrine tumors use these compounds as pharmacological tools to validate mechanistic hypotheses under controlled conditions.