Zollinger-Ellison syndrome is characterized by elevated blood levels of which peptide?

• A. Trypsin
• B. Pepsin
• C. Gastrin
• D. Cholecystokinin-pancreozymin

Answer: (C)

Zollinger-Ellison syndrome is driven by a gastrin-secreting tumor, so the key finding is markedly elevated gastrin levels in the blood. Gastrin is a peptide hormone produced by G cells in the stomach (and the proximal small intestine) that stimulates the gastric parietal cells to secrete hydrochloric acid, largely via histamine release from enterochromaffin-like cells. In this condition, the excess gastrin leads to gastric acid hypersecretion and peptic ulcers that are often refractory to standard therapy.

The other substances listed are not elevated in Zollinger-Ellison syndrome: trypsin and pepsin are digestive enzymes rather than circulating hormones associated with this syndrome, and cholecystokinin-pancreozymin is another gut hormone not characteristically increased in ZES.