sekretin

Sekretin, known in English as secretin, is a peptide hormone produced by S cells in the mucosa of the duodenum and proximal small intestine. It was one of the early hormones identified as a circulating regulator of distant organs. Secretin release is primarily triggered by acidic chyme entering the small intestine from the stomach.

Biochemistry and mechanism: Secretin is synthesized as part of a larger precursor called preprosecretin, which is processed to the active 27‑amino‑acid peptide. It acts by binding to the secretin receptor (SCTR), a class B G protein–coupled receptor located on pancreatic ductal cells, cholangiocytes, and other digestive tissues. Receptor activation stimulates adenylate cyclase, increases intracellular cAMP, and promotes secretion of bicarbonate- and water-rich fluid from the pancreas and bile ducts, helping to neutralize gastric acid in the lumen.

Physiological role: By enhancing pancreatic and biliary bicarbonate secretion, secretin creates an optimal pH for digestive enzymes to function. This acid-neutralizing mechanism complements other regulatory processes governing digestion and improves the efficiency of nutrient breakdown.

Clinical relevance: Secretin is used diagnostically in the secretin stimulation test to assess pancreatic exocrine function and ductal integrity, aiding evaluation of pancreatic insufficiency and certain biliary conditions. While not a routine therapeutic agent, secretin has a role in research and certain diagnostic protocols examining GI physiology and pancreatic health.