Overview
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In plain language
Secretin is a 27-amino-acid gut hormone that holds a historic title: it was the first hormone ever discovered, in 1902, which gave the entire field of endocrinology its name. It is used today as a diagnostic injection to test the pancreas.
In the 1990s it became famous in a different way, when parents reported that a secretin injection improved autism symptoms, triggering many rigorous studies. Those studies found no effect, and the episode is now taught as a case study in why controlled trials matter.
For students
Secretin is a 27-residue peptide hormone (about 3,056 Da) of the secretin family (glucagon, VIP, GIP, GLP-1 and GLP-2 are its structural cousins), released by S cells in the duodenum in response to acidic chyme. It acts on secretin receptors on pancreatic ductal and acinar cells, stimulating bicarbonate-rich pancreatic juice that neutralizes intestinal pH.
Synthetic human secretin (ChiRhoStim) is FDA-approved for stimulating the pancreas during diagnosis (e.g., imaging of pancreatic ducts and localizing gastrinomas via the secretin stimulation test). The autism episode is the instructive part: a 1998 case report of three children triggered widespread off-label use, and subsequent double-blind placebo-controlled trials (including a 1999 NEJM study of 60 children and a multi-site 2001 study of 128 children) found no benefit, establishing the standard of care and becoming a canonical teaching case in evidence-based medicine.
For researchers and instructors
Biochemistry. The secretin family's shared helix-bundle fold and the evolutionary relationship between GI hormones is the structural lesson; secretin's discovery by Bayliss and Starling in 1902, and Starling's coining of "hormone" (from the Greek for "to set in motion"), founded endocrine physiology.
Pharmacology. IV or intraduodenal dosing for diagnostic use; half-life minutes; rare hypersensitivity; current availability should be confirmed with the manufacturer (ChiRhoStim) when planning diagnostic use.
Human evidence. Diagnostic validation studies for pancreatic function testing; three double-blind randomized trials (n=60, 62 and 128) disproved the autism application, a textbook sequence from case report to refutation.
Teaching point. Teaches both the discovery of hormonal signaling as a concept and the disciplined response to an anecdote-driven treatment claim.
Molecular identity
- Amino acids
- 27
- Molecular weight
- ~3,056 Da
- Formula
- C₁₃₀H₂₂₀N₄₄O₃₇S
- Sequence
- HSDGTFTSELSRLRDSARLQRLLQGLV
Origin and history
Secretin holds a historic title: in 1902, Bayliss and Starling extracted it from the intestinal lining and found it travels in the blood to tell the pancreas to release juice, the discovery that Starling named 'hormone' (from Greek for messenger).
Synthetic porcine secretin (ChiRhoStim) is FDA-approved to test pancreatic function and to locate tumors during surgery. It also became a cautionary tale: it was promoted for autism in the 1990s and randomized trials showed no effect.
Key people
- William Bayliss and Ernest StarlingDiscovered secretin (1902)
Timeline
- 1902
Discovered; the word 'hormone' is coined
- 1960s
Secretin-based tests introduced
- 1990s
Autism claim disproven in trials
See every peptide on one history timeline.
Human evidence
Well-controlled diagnostic studies and multiple randomized trials that disproved the autism claim both inform its evidence base.
Registration and enrollment are not proof of benefit; check study results directly.
Explore original publications and distinguish preclinical findings from controlled human evidence.
Safety and regulatory status
See every compound on the regulatory tracker.
FDA-approved as a diagnostic aid. Rare allergic reactions; confirm current availability with the manufacturer.
This profile is educational and does not provide treatment, dosing or sourcing guidance.
Sources
- PubMed literature search: Secretin
- PubChem compound search: Secretin
- DailyMed (FDA label search): Secretin
- UniProt search: Secretin
- ClinicalTrials.gov search: Secretin
Hernandez Gener, E. (November 8, 2026). Secretin: molecular data, research history and evidence. VALREXA Biosciences. https://valrexa.com/peptides/secretin.html
APA style · Last reviewed November 8, 2026 · Our editorial standardsLast reviewed November 8, 2026. Trial and regulatory status can change; confirm in the linked registries. This profile is educational and is not medical advice, a treatment recommendation, or dosing or sourcing guidance. Report an error · Corrections policy