Gastrin
A hormone made in the stomach that drives acid production. It is measured mainly when a rare acid-overproducing tumour (a gastrinoma, causing Zollinger-Ellison syndrome) is suspected — for example with severe or recurrent ulcers — where the fasting level is very high.
What it measures
Gastrin is a hormone released by G-cells in the lining of the stomach and upper small intestine. Its job is to stimulate the stomach to produce acid, which helps digest food. The body normally keeps gastrin in balance: when the stomach is acidic, gastrin release is switched off, and when acid is low, gastrin rises to compensate. A fasting blood gastrin test is used mainly to investigate one specific problem: a gastrinoma, a rare neuroendocrine tumour that pumps out gastrin uncontrollably, driving massive acid production and causing Zollinger-Ellison syndrome (severe, multiple or recurrent peptic ulcers and diarrhoea). In that setting the fasting gastrin is markedly high while the stomach is still very acidic — a combination that distinguishes it from the far commoner, harmless causes of a raised gastrin. Those common causes are anything that lowers stomach acid, above all acid-suppressing medicines (proton-pump inhibitors), and also atrophic gastritis or infection with H. pylori, where gastrin rises appropriately because acid is low. Because these medicines strongly raise gastrin, the test is interpreted carefully and usually alongside a measure of stomach acidity.
What a high value can mean
- Acid-suppressing medication (proton-pump inhibitors) — the commonest cause of a raised gastrin; harmless and expected.
- Zollinger-Ellison syndrome (gastrinoma) — a very high gastrin with an acidic stomach; the key diagnosis the test looks for.
- Atrophic gastritis — reduced acid production drives gastrin up appropriately.
- H. pylori infection — can raise gastrin.
- Kidney impairment — reduced clearance.
What a low value can mean
- Normal or low — the expected result; not usually of clinical concern.
When to discuss with a doctor
A fasting gastrin is a targeted test, not a routine one — it is mostly ordered when severe, multiple or recurrent peptic ulcers, ulcers in unusual places, or ulcers with diarrhoea raise suspicion of a gastrinoma (Zollinger-Ellison syndrome). Because acid-suppressing medicines are by far the commonest reason for a high gastrin, the result must be read in the context of whether such drugs are being taken and how acidic the stomach is; a truly diagnostic result usually needs the medicine stopped under specialist guidance and confirmatory testing. Mediora.AI can surface a markedly raised gastrin from your results and flag the pattern for review, but sorting a harmless medication effect from a rare tumour is a specialist assessment — the interpretation belongs with your doctor.