Secretin
The first hormone ever described, now an approved diagnostic agent and nothing else
Secretin, released by the duodenum when acid arrives, was the discovery that created the word hormone. Synthetic human secretin is approved in the United States as a diagnostic agent. Trials that tried it as a treatment, in autism and in schizophrenia, did not find a benefit.
What is it?
Secretin is released by S-cells of the duodenum when stomach acid reaches it, and makes the pancreas pour out bicarbonate. Its discovery in 1902 is where the idea of a hormone, a chemical messenger carried in blood, began. It is a 27-amino-acid peptide acting on the secretin receptor.
In the United States it is approved only as a diagnostic agent. The ChiRhoStim label covers three uses: stimulating pancreatic secretion to test the exocrine pancreas, stimulating gastrin to help diagnose gastrinoma, and stimulating pancreatic secretion to make the ampulla of Vater easier to find during ERCP. The dose is 0.2 mcg/kg intravenously over one minute, or 0.4 mcg/kg for the gastrinoma test. The label gives its elimination half-life as 45 minutes, with plasma levels back to baseline within 90 to 120 minutes, far longer than the three to five minutes often quoted.
The gastrinoma test works because secretin paradoxically raises gastrin from these tumours. In a 2022 study of people with the inherited syndrome MEN1, the test was positive in 18 of 72 with gut or pancreatic neuroendocrine tumours, and it picked up stimulated hypergastrinaemia in 3 of 4 whose resting gastrin was normal, which is its value for early diagnosis.
Reading the test needs care, and the label says so. Acid-suppressing drugs can falsely suggest gastrinoma: a 2009 case report described a woman whose high gastrin and positive secretin test both normalised after her proton-pump inhibitor was stopped. The label tells clinicians to stop H2 blockers or proton-pump inhibitors before the gastrin test and anticholinergics at least five half-lives before testing, and warns that liver disease can mask pancreatic disease by exaggerating the response.
Secretin is also given during MRI of the pancreatic ducts (secretin-enhanced MRCP). In people with recurrent acute pancreatitis, secretin-enhanced images found ductal abnormalities more often than standard images (sensitivity 76% against 56%) and showed reduced exocrine function in 32% against 9% of controls. This imaging use is not one of the three uses on the US label.
Its time as a proposed treatment was short. After uncontrolled reports in autism, a 1999 New England Journal of Medicine trial gave 56 children a single dose of synthetic human secretin or placebo and found no improvement on any measure, and later trials of autism-related sleep and of refractory schizophrenia were also negative. Newer imaging studies in healthy volunteers show it acting on brown fat, appetite circuits, the heart and the kidney, which is physiology rather than a use.
Mechanism of Action
Secretin makes the pancreas release bicarbonate-rich fluid; in gastrinoma it raises gastrin, which is the basis of the diagnostic test.
Pancreatic bicarbonate
The pancreas responds with bicarbonate-rich fluid, which is what the pancreatic function test measures and what makes ducts and the ampulla visible during ERCP and MRCP.
Gastrin from gastrinomas
Gastrin-secreting tumours respond to secretin with a rise in gastrin; acid-suppressing drugs can mimic this, which is why they are stopped first (label).
Short diagnostic window
Given as one intravenous injection; plasma levels return to baseline within 90 to 120 minutes (label).
Published Research
The studies behind secretin, read from their PubMed abstracts: its diagnostic uses, the failed treatment trials and the newer physiology.
The secretin test for gastrinoma in MEN1
Secretin-induced hypergastrinaemia was found in 20 of 72 patients with gut or pancreatic neuroendocrine tumours, with 18 positive tests, and in 3 of 4 whose resting gastrin was normal.
Secretin-enhanced MRCP in recurrent pancreatitis
Secretin-enhanced images detected ductal abnormalities with higher sensitivity than standard images (76% against 56%) and showed reduced exocrine function in 32% of patients against 9% of controls.
Autism: a single dose against placebo, 56 children
Synthetic human secretin produced no significant improvement on any outcome over four weeks; behaviour-checklist scores fell 8.9 points on secretin and 17.8 on placebo.
A false-positive test on a proton-pump inhibitor
A case report of a 22-year-old woman with high gastrin and a positive secretin test while on a proton-pump inhibitor; both normalised after it was stopped. Earlier false positives had been reported only with atrophic gastritis.
Appetite, through brown fat
In a placebo-controlled imaging study, secretin changed brain glucose use through brown adipose tissue in 15 people, improved inhibitory control and damped the brain's response to pictures of appetising food in 14, with a combined analysis in 10 linking the two.
Heart and kidney effects in healthy men
In a placebo-controlled crossover study in 15 healthy fasting men, secretin raised heart-muscle glucose uptake (15.5 against 9.7 µmol/100 g/min, p = 0.004) and kidney clearance, and raised estimated glomerular filtration rate against placebo (p = 0.001).
No benefit in schizophrenia
Twenty-two patients with treatment-refractory schizophrenia were randomised to a single intravenous dose of porcine secretin or placebo and followed for four weeks. There was no statistically significant difference between the groups on either symptom scale.
No effect on sleep in autism
A sleep study nested in two double-blind placebo-controlled trials in children with autism, using sleep questionnaires, diaries and home video recording, found that neither porcine nor synthetic human secretin improved sleep.
Dosing Data
ChiRhoStim is given once, intravenously over one minute, at a dose set by body weight and the test being done.
Educational information, not medical advice. Each dose above is tagged with its source: an approved label, a published human study, animal data, or amounts reported by users. None is a recommendation for you. An unapproved compound has no established safe or effective human dose, and products sold for “research use only” are not made or tested for people. Talk to a doctor before acting on anything on this site, including before you start, stop or change any medicine or dose. Full medical disclaimer.
Side Effects & Contraindications
Reported Side Effects
From the ChiRhoStim prescribing information (DailyMed set b4dfe70f, effective October 8, 2025).
Contraindications & Cautions
From the label.
Legal Status
Approved, but only to make a diagnosis.
Frequently Asked Questions
?What is secretin used for?
Three diagnostic jobs, all on its label: testing how the pancreas secretes, helping diagnose gastrinoma, and making the ampulla of Vater easier to find during ERCP.
?How long does it last?
The ChiRhoStim label gives an elimination half-life of 45 minutes, with plasma levels back to baseline within 90 to 120 minutes.
?Does secretin treat autism?
No. Controlled trials followed the early uncontrolled reports and found no benefit, including on sleep.
?Why is secretin historically important?
Its discovery in 1902 established that the body sends chemical messengers through the blood, which is what the word hormone was coined to describe.
?Can medicines affect the test?
Yes. The label says proton-pump inhibitors and H2 blockers can falsely raise gastrin and suggest gastrinoma, so they are stopped beforehand, and anticholinergics are stopped at least five half-lives before testing because they blunt the response.
?How good is the gastrinoma test?
In a 2022 study of people with MEN1, it was positive in 18 of 72 with gut or pancreatic neuroendocrine tumours and found stimulated hypergastrinaemia in 3 of 4 whose resting gastrin was normal, which is why it is used for earlier diagnosis.
?Does secretin act outside the gut?
In healthy men it raised heart-muscle glucose uptake and kidney filtration in a placebo-controlled study, and in another it changed brain responses to food through brown fat. These are research findings, not uses.
?Is secretin used in MRI scans?
Yes, in secretin-enhanced MRCP, which showed more ductal abnormalities than standard images in recurrent pancreatitis; this use is not on the US label.
?What doses are used?
0.2 mcg/kg intravenously over one minute for pancreatic function testing and ERCP, and 0.4 mcg/kg for the gastrinoma test (label).
References
- [fda-pi] ChiRhoStim (human secretin) prescribing information, sections 1, 2, 5 and 12.3 (DailyMed SPL effective October 8, 2025; read October 1, 2026).
- [pubmed] Giusti F, et al. "Secretin Stimulation Test and Early Diagnosis of Gastrinoma in MEN1 Syndrome: Survey on the MEN1 Florentine Database." J Clin Endocrinol Metab, 2022;107(5):e2110-e2123. PMID: 34922358.
- [pubmed] Sandrasegaran K, et al. "The Value of Secretin-Enhanced MRCP in Patients With Recurrent Acute Pancreatitis." AJR Am J Roentgenol, 2017;208(2):315-321. PMID: 27824485.
- [pubmed] Sandler AD, et al. "Lack of benefit of a single dose of synthetic human secretin in the treatment of autism and pervasive developmental disorder." N Engl J Med, 1999;341(24):1801-6. PMID: 10588965.
- [pubmed] Goldman JA, et al. "False-positive secretin stimulation test for gastrinoma associated with the use of proton pump inhibitor therapy." Clin Gastroenterol Hepatol, 2009;7(5):600-2. PMID: 19245850.
- [pubmed] Sun L, et al. "Secretin modulates appetite via brown adipose tissue-brain axis." Eur J Nucl Med Mol Imaging, 2023;50(6):1597-1606. PMID: 36764966.
- [pubmed] Laurila S, et al. "Novel effects of the gastrointestinal hormone secretin on cardiac metabolism and renal function." Am J Physiol Endocrinol Metab, 2022;322(1):E54-E62. PMID: 34806426.
- [pubmed] Sheitman BB, et al. "Secretin for refractory schizophrenia." Schizophr Res, 2004;66(2-3):177-81. PMID: 15061251.
- [pubmed] Honomichl RD, et al. "Secretin and sleep in children with autism." Child Psychiatry Hum Dev, 2002;33(2):107-23. PMID: 12462350.
- [pubmed] Bayliss WM, et al. "The mechanism of pancreatic secretion." J Physiol, 1902;28(5):325-53. PMID: 16992627.
- [pubmed] Afroze S, et al. "The physiological roles of secretin and its receptor." Ann Transl Med, 2013;1(3):29. PMID: 25332973.
Sources & Citations
Studies were read from their PubMed records (October 5, 2026); the label and Drugs@FDA are listed below with their read dates.
Medical Disclaimer: This content is for educational and informational purposes only. It is not medical advice, and nothing here is an instruction to obtain or use any compound. Talk to a licensed clinician about your own situation.