Gastrin-secreting cells (G-cells) produce, store and release gastrin within the pyloric and upper duodenal mucosa. Gastrin stimulates gastric acid secretion by parietal cells and circulates in 2 active forms: gastrin-34 (G-34) and gastrin-17 (G-17).
Determination of circulating gastrin concentrations can aid in the diagnosis of gastrinoma. Greater than 50% are malignant and approximately 25% occur as part of multiple endocrine neoplasia type 1 (MEN 1). The presence of gastrinoma and hypergastrinaemia resulting in severe refractory peptic ulcer disease is known as Zollinger-Ellison syndrome.
Increased circulating gastrin concentrations can also occur as a result of reduced or absent gastric acid secretion e.g. H pylori infection, chronic atrophic gastritis +/- pernicious anaemia or long-term use of proton pump inhibitors (PPIs). This is due to the lack of inhibitory feedback of acid on the G-cells. Therefore elevated gastrin levels should be interpreted in relation to gastric acid secretion.
Sample Requirements and Reference Ranges
|| Heparinised plasma (EDTA unsuitable)
|| Sample should be collected after an overnight fast. Separate and freeze plasma. Transport frozen. Proton pump inhibitors should be discontinued for a week, and H2 blockers for 48 hours, prior to sampling. Icterus and lipaemia moderately reduce results.
|| 1 mL
|| <115 ng/L (fasting)
|| 35 days
|| Siemens Immulite. This assay measures both the G-17 isoform and, to a lesser extent, the G-34 isoform.