gastrin

Gastrin is the stomach’s “turn on the acid” signal. When food arrives or the stomach stretches, specialized cells release gastrin, which travels in the blood and tells acid-producing cells to start working — preparing the stomach to break down protein.

Gastrin is a peptide hormone secreted by G-cells, mostly in the stomach’s antrum (its lower portion). It stimulates parietal cells to secrete hydrochloric acid, both directly and indirectly by triggering release of histamine from nearby cells. It also promotes growth of the stomach lining. Its release is driven by food (especially protein), stomach distension, and nerve signals, and it is switched off by the very acid it helps produce — a classic negative-feedback arrangement.

Clinically, gastrin matters because a rare tumor (gastrinoma, seen in Zollinger-Ellison syndrome) secretes excessive gastrin, causing relentless acid and severe ulcers. Acid-suppressing drugs like proton-pump inhibitors raise gastrin levels by removing the acid that normally restrains it — usually harmless, but worth knowing when interpreting blood tests.