# Secretin > The first hormone ever discovered — the 1902 gut peptide that coined the word "hormone"; today a diagnostic agent for the pancreas. - Also known as: ChiRhoStim, human secretin - Class: Peptide Hormones - FDA approved: No - Canonical page: https://americanpeptide.com/catalog/secretin ## Overview Secretin is a 27-amino-acid hormone of the upper small intestine that signals the pancreas and bile ducts to release bicarbonate-rich fluid, neutralizing stomach acid as it enters the duodenum. Its historical importance is hard to overstate: discovered by Bayliss and Starling in 1902, it was the first chemical messenger ever identified, and Starling coined the very word "hormone" to describe it. Synthetic human secretin (ChiRhoStim) is used today mainly as a diagnostic stimulant in pancreatic-function and imaging tests. Secretin is where endocrinology begins. In 1902 William Bayliss and Ernest Starling showed that acid in the small intestine triggers pancreatic secretion even when all the nerves are cut — proof that a blood-borne chemical, not a nerve, carried the message. Starling later named this new class of messengers "hormones," from the Greek for "to set in motion." Secretin is therefore both a working hormone and the founding object of the entire field, which is reason enough for it to anchor this category historically. Physiologically it is a bicarbonate hormone. Released by S-cells of the duodenum when acidic chyme arrives, secretin drives the pancreas and bile ducts to pour out an alkaline, bicarbonate-rich fluid that protects the intestinal lining and creates the neutral pH that digestive enzymes need. It belongs to the secretin/glucagon/VIP superfamily, sharing a structural template with several other gut and metabolic hormones in this catalog. Its modern role is diagnostic rather than therapeutic. Synthetic human secretin is given to stimulate pancreatic output during function testing and secretin-enhanced MRCP imaging, and to provoke gastrin release in the diagnosis of gastrinoma (Zollinger–Ellison syndrome). A once-fashionable hypothesis that secretin might treat autism was tested in controlled trials and clearly failed — a useful, honest footnote to a hormone whose real value is as a precise diagnostic tool. ## Mechanism Agonist at the secretin receptor (a class B GPCR) on pancreatic duct and biliary cells, raising cAMP and stimulating secretion of water and bicarbonate. It also modestly inhibits gastric acid and gastric emptying. ## Chemistry | Property | Value | | --- | --- | | Molecular weight | 3039.4 Da | ## Sequence ``` HSDGTFTSELSRLREGARLQRLLQGLV (C-terminal amide; human) ``` ## Research areas Studied in: Pancreatic function testing, Gastrointestinal physiology, Gastrinoma diagnosis, Peptide hormones. Guides on this site: - [Peptide Hormone Synthesis](https://americanpeptide.com/research-areas/peptide-hormones): How hormone sequences are turned into pure, stable, manufacturable synthetic drugs. ## Key research - Historical first — the first hormone ever discovered (Bayliss & Starling, 1902); the molecule that gave the word "hormone" to science. - Pancreatic-function testing — synthetic secretin stimulates pancreatic bicarbonate output, used in function tests and secretin-enhanced MRCP. - Gastrinoma diagnosis — the secretin stimulation test paradoxically raises gastrin in Zollinger–Ellison syndrome, aiding diagnosis. - Bicarbonate physiology — duodenal S-cells release it in response to acid, triggering alkaline pancreatic/biliary secretion. - Autism hypothesis refuted — controlled trials of secretin for autism showed no benefit, a clear negative result. ## Storage, handling & synthesis **Synthesis.** A 27-residue C-terminal-amide peptide of the secretin/glucagon/VIP family, made by solid-phase synthesis with a terminal amidation step. The meaningful modern change is provenance rather than chemistry: the clinical agent (synthetic human secretin, ChiRhoStim) replaced earlier porcine material extracted from animal tissue. That shift — from variable animal extract to a defined, sequence-verified synthetic product with a certificate of analysis — is the core quality story for older hormone peptides and exactly the transparency this catalog tracks. ## FAQs ### What does secretin do? It signals the pancreas and bile ducts to release bicarbonate-rich fluid that neutralizes stomach acid entering the small intestine. It is released by the duodenum in response to acid. ### Why is secretin historically important? It was the first hormone ever discovered (1902), and its discovery prompted Ernest Starling to coin the word "hormone." It effectively founded the science of endocrinology. ### What is secretin used for now? Mainly diagnosis — stimulating pancreatic secretion for function tests and MRCP imaging, and provoking gastrin release to diagnose gastrinoma. A past idea that it could treat autism was tested and disproven. ### Is this medical advice? No — this is a research and educational reference, not dosing guidance. ## Latest research Recent trials and publications mentioning Secretin, pulled automatically from ClinicalTrials.gov and PubMed (unfiltered search results, refreshed daily). ### Recent trials - [The LINFU® U.S. Registry in Patients With IPMN (Intraductal Papillary Mucinous Neoplasm of the Pancreas)](https://clinicaltrials.gov/study/NCT06276764) — ENROLLING_BY_INVITATION · NCT06276764 - [Evaluation of Pirfenidone as a Novel Therapeutic Strategy Against Recurrent Acute Pancreatitis.](https://clinicaltrials.gov/study/NCT06253117) — RECRUITING · PHASE2 · NCT06253117 - [A Study Of Effect Of Secretin For In Injection (Chirostim) On Pancreatic Fluid Composition In Healthy Subjects](https://clinicaltrials.gov/study/NCT07285863) — RECRUITING · PHASE4 · NCT07285863 - [Metabolic Phenotyping for Personalized Obesity Therapy](https://clinicaltrials.gov/study/NCT06874270) — TERMINATED · NCT06874270 - [Secretin in Ex-situ Liver Perfusion](https://clinicaltrials.gov/study/NCT07651748) — ENROLLING_BY_INVITATION · PHASE1, PHASE2 · NCT07651748 - [Food Intake, Endocrine Factors and Brown Fat](https://clinicaltrials.gov/study/NCT06285461) — ACTIVE_NOT_RECRUITING · NA · NCT06285461 --- Source: AmericanPeptide.com — https://americanpeptide.com/catalog/secretin Data license: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Attribution: AmericanPeptide.com. Research reference only — computational and educational content, not medical advice.