Peptide Basics
Gastrin: The Stomach-Acid Hormone, Its Six Forms, Its Receptor and What FDA Records Show
Gastrin is a peptide hormone made by G cells in the lower part of the stomach; it tells the stomach lining to produce and release acid, and it is released when food arrives and held back as acid builds up. This page sets out how one precursor yields six gastrins, what gastrin shares with cholecystokinin, how the acid signal is passed on and switched off, why gastrin rises with acid-lowering medicines and in gastrinoma, and which gastrin-related products appear in FDA’s records. Every figure is taken from UniProt, PubChem, MeSH, PubMed, MedlinePlus or FDA’s own databases and labels.
What gastrin is
MeSH, the U.S. National Library of Medicine’s subject index, describes the gastrins as a family of gastrointestinal peptide hormones that excite the secretion of gastric juice, and adds that they may also occur in the central nervous system, where they are presumed to act as neurotransmitters. UniProt gives the fuller list of actions: gastrin stimulates the stomach lining to produce and secrete hydrochloric acid and the pancreas to secrete its digestive enzymes; it also stimulates smooth muscle contraction and increases blood circulation and water secretion in the stomach and intestine. It is one of the peptide hormones.
The cells that make it are called G cells. MeSH places them predominantly in the gastric glands of the pyloric antrum, the lower part of the stomach before it opens into the duodenum, and notes that they are also found in the duodenum and in nervous and other tissues.
Gastrin has a long paper trail. PubMed indexes J. S. Edkins’s 1906 paper “The chemical mechanism of gastric secretion” in the Journal of Physiology (PMID 16992839), and two 1964 papers by Gregory and Tracy in Gut: one on the constitution and properties of two gastrins extracted from hog antral mucosa (PMID 14159395) and one on the gastrin-like stimulant present in Zollinger-Ellison tumours (PMID 14159397). PubMed holds these older records without abstracts, so we cite them by title only.
Sources: MeSH D005755, D019863 and D011706; UniProt P01350; PubMed 16992839, 14159395, 14159397. Read 11 November 2026.
One precursor, six gastrins: gastrin-17, gastrin-34 and the rest
Every form of gastrin is cut from a single 101-amino-acid precursor made by the GAST gene. All six forms end at the same place, position 92, so each shorter gastrin is the tail end of the longer ones. UniProt maps the precursor like this:
| Piece | Positions | Amino acids | Note |
|---|---|---|---|
| Signal peptide | 1-21 | 21 | Steers the precursor into the cell's export route; removed first. |
| Gastrin-71 | 22-92 | 71 | The longest form; UniProt describes a possible second processing route that produces it. |
| Gastrin-52 | 41-92 | 52 | A shorter form that starts at position 41. |
| Big gastrin (gastrin-34) | 59-92 | 34 | One of the two major active forms. Its first amino acid is closed into a ring (pyroglutamate). |
| Gastrin (gastrin-17) | 76-92 | 17 | QGPWLEEEEEAYGWMDF: the other major active form, also with a ring-closed first amino acid. |
| Gastrin-14 | 79-92 | 14 | WLEEEEEAYGWMDF. |
| Gastrin-6 | 87-92 | 6 | YGWMDF, the shortest form UniProt lists. |
| Propeptide | 96-101 | 6 | The tail of the precursor, removed in the mature forms. |
UniProt records that in the main processing route of the antral G cell the precursor is cut at three sites, giving two major active gastrins, gastrin-34 and gastrin-17. Every form carries an amide on its final phenylalanine. The tyrosine at position 87 can carry a sulfate group, but only in part of the molecules: UniProt records that gastrin-6 is almost 73 per cent sulfated, while the larger gastrins are less than 50 per cent sulfated. PubChem gives gastrin-17 the formula C97H124N20O31S and a molecular weight of 2,098.2 (CID 16162108). The first 21 amino acids of the precursor are a signal sequence, explained on our signal peptides page.
Sources: UniProt P01350; PubChem CID 16162108. Read 11 November 2026.
Gastrin and cholecystokinin: one family, one shared receptor
UniProt files gastrin in the gastrin/cholecystokinin family. The two hormones come from different genes and do different jobs, but they end in the same five amino acids:
| Feature | Gastrin | Cholecystokinin (CCK) |
|---|---|---|
| Gene and precursor | GAST; 101 amino acids | CCK; 115 amino acids |
| Forms UniProt lists | Gastrin-71, -52, -34, -17, -14 and -6 | Cholecystokinin-58, -39, -33, -25, -18, -12, -8, -7 and -5, plus a shortened form of cholecystokinin-58 |
| Last five amino acids | GWMDF, with an amide on the final phenylalanine | GWMDF, with an amide on the final phenylalanine |
| Sulfated tyrosine | Tyrosine 87, sulfated in only part of the molecules | Tyrosine 97, the second amino acid of cholecystokinin-8 |
| Where MeSH places it | G cells, mainly in the glands of the pyloric antrum of the stomach | The lining of the upper intestine; also the central nervous system |
| Main action in MeSH | Excites the secretion of gastric juice | Gallbladder contraction and release of pancreatic digestive enzymes |
The two hormones also share a receptor. UniProt names it the gastrin/cholecystokinin type B receptor, also called the cholecystokinin-2 receptor (gene CCKBR): a 447-amino-acid G protein-coupled receptor for both hormones. MeSH places it primarily in the central nervous system and the gastric mucosa; UniProt records that within the stomach it is expressed at high levels in the mucosa of the fundus and at low levels in the antrum and duodenum. When the receptor was cloned from dog parietal cells in 1992, the authors found its transcripts in both parietal cells and the cerebral cortex and concluded that the stomach’s gastrin receptor and the brain’s CCK-B receptor are either highly homologous or identical (PMID 1373504).
Sources: UniProt P01350, P06307 (CCK) and P32239 (CCKBR); MeSH D002766 and D043887; PubMed 1373504. Read 11 November 2026.
How gastrin drives stomach acid, and what switches it off
The public records describe a loop with a start signal, a relay and a brake:
- Start: MedlinePlus states that when there is food in the stomach, gastrin is released into the blood. UniProt records that gastrin-releasing peptide, a separate peptide, stimulates the release of gastrin.
- Relay: MeSH records that enterochromaffin-like cells in the stomach lining respond to gastrin by releasing histamine, which acts locally to stimulate the release of hydrochloric acid from the parietal cells. The parietal cells, in MeSH’s description, secrete hydrochloric acid and produce intrinsic factor, the protein that binds vitamin B12.
- Brake: MedlinePlus states that as the acid level rises in the stomach and intestines, the body normally makes less gastrin. MeSH records that the somatostatin-secreting D cells of the gut hold gastrin back; that hormone has its own page, somatostatin.
Sources: MedlinePlus Medical Encyclopedia, “Gastrin blood test” (reviewed 13 July 2025); UniProt P07492 (gastrin-releasing peptide; the statement is marked by similarity); MeSH D019861, D010295 and D019864. Read 11 November 2026.
When gastrin is high: acid-lowering medicines and gastrinoma
Acid-lowering medicines raise gastrin, and their labels say so. The U.S. label of the proton pump inhibitor Prilosec (omeprazole) states that in studies involving more than 200 patients, serum gastrin levels increased during the first one to two weeks of once-daily treatment, in parallel with the inhibition of acid secretion; that no further increase occurred with continued treatment; that the median increases were higher than those seen with histamine H2 blockers; and that gastrin values returned to pretreatment levels, usually within one to two weeks after treatment stopped. MedlinePlus lists antacids, H2 blockers and proton pump inhibitors among the medicines that can raise the gastrin level.
The other well-documented cause is a tumour that makes gastrin. MeSH describes a gastrinoma as a gastrin-secreting neuroendocrine tumour located primarily in the pancreas or the duodenum, records that the majority are malignant, and notes that it sometimes occurs in families with multiple endocrine neoplasia type 1. Zollinger-Ellison syndrome, in MeSH’s wording, is the triad of severe peptic ulcer, hypersecretion of gastric acid and a gastrin-producing tumour. The syndrome carries the names of the authors of a 1955 paper in Annals of Surgery, Zollinger and Ellison’s “Primary peptic ulcerations of the jejunum associated with islet cell tumors of the pancreas” (PMID 13259432). MedlinePlus lists further conditions linked to a higher gastrin level, among them long-term gastritis, Helicobacter pylori infection of the stomach, chronic kidney disease and a decreased ability of the stomach to produce acid.
This section describes published records. It gives no reference ranges and does not interpret a test result; that belongs with the laboratory and the clinician who ordered the test.
Sources: Prilosec U.S. label (NDA 022056, label dated March 2024), section on serum gastrin effects; MedlinePlus Medical Encyclopedia, “Gastrin blood test”; MeSH D015408 and D015043; PubMed 13259432 (title only; no abstract). Read 11 November 2026.
Gastrin in FDA’s records
Gastrin itself is not an approved medicine: a search of Drugs@FDA by active ingredient on 11 November 2026 returned no product for gastrin, and none for the gastrin-receptor blockers netazepide or proglumide. Three related records do exist. The table lists each by the approval year recorded for its original application:
| Product | Application | Approved | What it is and how it relates to gastrin |
|---|---|---|---|
| Peptavlon (pentagastrin) | NDA 017048 | 1974 | A synthetic five-amino-acid relative of gastrin. MeSH records that it stimulates the secretion of gastric acid, pepsin and intrinsic factor and has been used as a diagnostic aid. Drugs@FDA lists it as discontinued, with FDA's note that it was not withdrawn for safety or effectiveness reasons. |
| ChiRhoStim (human secretin) | NDA 021256 | 2004 | Not gastrin, but a peptide hormone used to test for it: the label's indications include stimulating gastrin secretion to aid in the diagnosis of gastrinoma. The label warns that H2 blockers and proton pump inhibitors can cause an exaggerated gastrin response that falsely suggests gastrinoma. |
| Prilosec (omeprazole) | NDA 019810; NDA 022056 | 1989; 2008 | Not a peptide and not a gastrin blocker: it blocks the acid pump of the parietal cell. The current label is indicated for long-term treatment of pathological hypersecretory conditions such as Zollinger-Ellison syndrome in adults, and describes how serum gastrin rises during treatment. The 1989 capsule application is listed as discontinued. |
Pentagastrin is the only one of the three built from gastrin, and it is small: PubChem gives it the formula C37H49N7O9S and a molecular weight of 767.9 (CID 9853654), against 2,098.2 for gastrin-17. The table is not a list of every acid-lowering product; Drugs@FDA holds dozens of omeprazole applications alone, and the Prilosec label is used here because it describes the effect on gastrin.
Sources: Drugs@FDA via openFDA, searched by active ingredient (original approval dates; data updated 9 November 2026); current U.S. labels for ChiRhoStim (October 2025) and Prilosec (March 2024); MeSH D010418; PubChem CID 9853654 and 16162108. Read 11 November 2026. Doses are not reproduced here; the approved medicines that are themselves peptides are on our FDA-approved peptides page.
Medibact does not manufacture or sell peptides. We supply USP-grade bacteriostatic water, made in the USA, for research use only, and publish reference material like this page.
Where this sits in the rest of the reference
FAQ
What is gastrin?
Gastrin is a peptide hormone of the stomach. MeSH describes the gastrins as a family of gastrointestinal peptide hormones that excite the secretion of gastric juice. They are cut from one 101-amino-acid precursor made by the GAST gene; UniProt names gastrin-34 and gastrin-17 as the two major active forms.
What does gastrin do?
UniProt records that gastrin stimulates the stomach lining to produce and secrete hydrochloric acid and the pancreas to secrete its digestive enzymes, and that it also stimulates smooth muscle contraction and increases blood circulation and water secretion in the stomach and intestine. MedlinePlus calls it the main hormone that controls the release of acid in the stomach.
Where is gastrin produced?
In G cells. MeSH places these endocrine cells predominantly in the gastric glands of the pyloric antrum, the lower part of the stomach, and notes that they are also found in the duodenum and in nervous and other tissues.
What triggers the release of gastrin?
Food in the stomach. MedlinePlus states that gastrin is released into the blood when there is food in the stomach, and that the body normally makes less gastrin as the acid level rises. UniProt records that gastrin-releasing peptide stimulates the release of gastrin, and MeSH records that the somatostatin-secreting D cells of the gut hold it back.
What is the difference between gastrin-17 and gastrin-34?
Length. Gastrin-34, also called big gastrin, covers positions 59 to 92 of the precursor; gastrin-17 covers positions 76 to 92, so it is the last 17 amino acids of gastrin-34. Both end in the same amidated phenylalanine and both begin with a ring-closed amino acid. PubChem gives gastrin-17 the formula C97H124N20O31S and a molecular weight of 2,098.2.
How are gastrin and cholecystokinin related?
They belong to one family. UniProt files gastrin in the gastrin/cholecystokinin family, both hormones end in the same five amino acids, GWMDF, with an amide on the last one, and both bind the same receptor, which UniProt names the gastrin/cholecystokinin type B receptor (also called the cholecystokinin-2 receptor).
Does omeprazole increase gastrin?
The U.S. label says it does. The Prilosec label states that in studies involving more than 200 patients, serum gastrin levels increased during the first one to two weeks of once-daily treatment, in parallel with the inhibition of acid secretion, with no further increase on continued treatment, and that gastrin values returned to pretreatment levels usually within one to two weeks after stopping. This page reports the label; decisions about a medicine belong with the prescriber.
What are gastrinoma and Zollinger-Ellison syndrome?
MeSH describes a gastrinoma as a gastrin-secreting neuroendocrine tumour found mainly in the pancreas or the duodenum, and Zollinger-Ellison syndrome as the triad of severe peptic ulcer, hypersecretion of gastric acid and a gastrin-producing tumour. The syndrome carries the names of Zollinger and Ellison, the authors of a 1955 paper in Annals of Surgery. This page describes those records and gives no advice on diagnosis or treatment.
Is gastrin used as a medicine?
Not gastrin itself: a search of Drugs@FDA by active ingredient on 11 November 2026 returned no product for gastrin. Its synthetic five-amino-acid relative pentagastrin was approved in 1974 as Peptavlon and is now listed as discontinued; MeSH records that it has been used as a diagnostic aid. Human secretin (ChiRhoStim) is labelled for stimulating gastrin secretion to aid in the diagnosis of gastrinoma.
Is this medical advice?
No. This page explains what gastrin is, from public scientific and regulatory sources. It gives no dose, schedule, reference range or recommendation, and it does not interpret test results; anyone with a gastrin result or a medicine named here should follow their own clinician and product label. Peptides sold for research are labelled research use only, not for human use. Medibact supplies USP-grade bacteriostatic water, made in the USA, and is not affiliated with any manufacturer of the products named here.
References: UniProt P01350, P06307, P32239, P07492; MeSH D005755, D019863, D019861, D010295, D043887, D002766, D010418, D015043, D015408, D019864, D011706; PubChem CID 16162108 and 9853654; PubMed 16992839, 13259432, 14159395, 14159397, 1373504; MedlinePlus Medical Encyclopedia, “Gastrin blood test”; Drugs@FDA via openFDA and the current U.S. labels named above. Read 11 November 2026.
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