Gastrin is a peptide hormone primarily responsible for enhancing gastric mucosal growth, gastric motility, and secretion of hydrochloric acid (HCl) into the stomach. It is present in G cells of the gastric antrum and duodenum. Gastrin is primarily released in response to vagal and gastrin-releasing peptide (GRP) stimulation secondary to the ingestion of peptides, amino acids, gastric distention, and an elevated stomach pH. Conversely, gastrin release is decreased in response to paracrine inhibition by somatostatin and decreased stomach pH.
Gastrin is secreted into the blood and carried to the gastric fundus and cardiac, where the majority of HCl secreting parietal cells are found. HCl is necessary for the conversion of inactive pepsinogen to active pepsin, which helps with protein digestion in the stomach and the release of cobalamin (vitamin B12) from its salivary R-protein carrier. The main clinical indication for assaying gastrin is to diagnose a gastrin-producing tumor, gastrinoma. Also, there appears to be data emerging that suggests gastrin might have a role in certain cancers, such as gastric cancer.
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