gastrin

Gastrin is a peptide hormone produced mainly by G cells of the gastric antrum and, to a lesser extent, by the duodenal mucosa. It stimulates gastric acid secretion by parietal cells and promotes growth of the gastric mucosa.

Gastrin is synthesized as preprogastrin, processed to progastrin, and then to active forms such as gastrin-17, gastrin-34, and gastrin-52. The biologically active peptides share a C-terminal amide essential for receptor binding. Gastrin acts primarily via the cholecystokinin-B (CCK-B) receptor on enterochromaffin-like cells and parietal cells, with ECL-derived histamine amplifying acid secretion.

Release of gastrin is triggered by intraluminal peptides and amino acids, stomach distension, and vagal stimulation mediated by gastrin-releasing peptide. Secretion is inhibited by low pH; somatostatin released from D cells provides negative feedback.

Physiologically, gastrin stimulates acid secretion and contributes to mucosal growth. Clinically, elevated gastrin levels or gastrin-secreting tumors cause Zollinger-Ellison syndrome, characterized by excessive acid production and refractory peptic ulcers. Diagnosis uses fasting serum gastrin measurements and secretin stimulation tests, with imaging and localization of tumors as needed. Treatment focuses on controlling acid production with proton pump inhibitors and removing or managing gastrinomas as appropriate.