Gastriin

Gastriin, commonly known as gastrin, is a peptide hormone produced by G cells in the lining of the stomach, primarily in the antrum, with smaller amounts secreted in the duodenum. It exists in several active forms, the most abundant being gastrin-17 (G-17) and gastrin-34 (G-34). Gastrin is released in response to luminal peptides, amino acids, stomach distension, and vagal stimulation.

Gastrin's main actions are to stimulate gastric acid secretion and promote growth of the gastric mucosa. It binds to cholecystokinin B receptors (CCK-B receptors) on enterochromaffin-like (ECL) cells and, to a lesser extent, directly on parietal cells. Stimulation of ECL cells increases histamine release, which then acts on parietal cells to boost hydrochloric acid (HCl) secretion. Gastrin also has trophic effects, supporting the maintenance and growth of the gastric mucosa and ECL cell population, and it can modestly influence gastric motility.

Regulation of gastrin involves both stimulatory and inhibitory signals. Acid in the stomach provides negative feedback that suppresses gastrin release via somatostatin from D cells. Peptides, amino acids, and stomach distension during meals promote gastrin release, and vagal inputs via gastrin-releasing peptide (GRP) further enhance secretion.

Clinical relevant aspects include hypergastrinemia, which can arise from gastrin-secreting tumors (gastrinomas) causing Zollinger-Ellison syndrome, or from conditions that reduce stomach acidity, such as autoimmune gastritis or prolonged acid-suppressing therapy. Low gastrin levels may occur in achlorhydria due to other diseases. Gastrin levels are sometimes measured to evaluate acid-related disorders.