What it is
Secretin is a 27-amino-acid peptide hormone made in the first part of the small intestine, the duodenum, that tells the pancreas to release bicarbonate and neutralise stomach acid. UniProt (P09683) places it in the S cells of the duodenum and records a 121-residue precursor from which residues 28–54 are cut:
H-S-D-G-T-F-T-S-E-L-S-R-L-R-E-G-A-R-L-Q-R-L-L-Q-G-L-V-NH2, the final valine amidated.
The synthetic drug ChiRhoStim carries exactly this sequence; its label gives the formula C130H220N44O39 and molecular weight 3,039.44.
Its discovery
Secretin has a place in the history of physiology. In "The mechanism of pancreatic secretion" (J Physiol, 12 September 1902; PMID 16992627), W. M. Bayliss and E. H. Starling reported that a substance from the intestinal lining, travelling in the blood, could switch on the pancreas. That showed a chemical messenger at work, separate from nerves.
How it works
UniProt's annotation describes secretin as regulating the pH of the duodenal contents, food intake and water balance, through the secretin receptor (SCTR), a G-protein-coupled receptor on several cell types. The pancreas answers with juice rich in bicarbonate, which neutralises the acid arriving from the stomach.
Secretin gives its name to a family of peptide hormones that includes VIP and glucagon. The orexin entry records that one group named those brain peptides "hypocretins" partly for their resemblance to secretin.
As a diagnostic drug
| ChiRhoStim indication (label) | Labelled dose (for reference) |
|---|---|
| Pancreatic secretion, including bicarbonate, to aid diagnosis of exocrine pancreas dysfunction | 0.2 mcg/kg IV over 1 minute |
| Gastrin secretion to aid diagnosis of gastrinoma | 0.4 mcg/kg IV over 1 minute |
| Identifying the ampulla of Vater and accessory papilla during ERCP | 0.2 mcg/kg IV over 1 minute |
One clinical unit of secretin activity equals 0.2 mcg (label). The label also states that its reference figures come from investigators skilled in the test and "should not be generalized" to other laboratories.
What distorts the test (label warnings):
- Acid-suppressing drugs (H2 blockers, proton-pump inhibitors) raise gastrin and can falsely suggest gastrinoma.
- Liver disease can produce an exaggerated pancreatic response that masks pancreatic disease.
- Vagotomy, inflammatory bowel disease and anticholinergic drugs can blunt the response.
Every result is interpreted by the clinician who ordered it; this entry gives no reference ranges.
Safety
In the label's open-label trial of 531 patients, mostly given a single dose of 0.2–0.4 mcg/kg, the reactions seen in at least two patients were nausea (9), vomiting (3), flushing (2) and upset stomach (2).
The autism claim
In 1998 secretin was proposed as a treatment for autism on anecdotal evidence. The trials followed. The Cochrane review (Williams, Wray and Wheeler, 2012; PMID 22513913) found 16 randomised placebo-controlled trials with over 900 children; the results were consistent in showing no improvement in the core features of autism. Its conclusion: "There is no evidence that single or multiple dose intravenous secretin is effective and as such currently it should not be recommended or administered as a treatment for ASD." PubMed holds 126 records matching secretin and autism (2026-10-11).
Where it stands
- Made by the body; not a product in its own right.
- Synthetic human secretin approved since 2004-04-09 (ChiRhoStim, ChiRhoClin, NDA 021256), two strengths listed as prescription intravenous products (Drugs@FDA, 2026-10-11).
- Research record: PubMed indexes 9,177 records, 103 tagged as randomised trials (2026-10-11).
Related reading
Secretin is often given with sincalide, the synthetic tip of cholecystokinin, for pancreatic testing, and its gastrinoma test measures gastrin. Somatostatin and its drug copy octreotide suppress secretin release.