A patient diagnosed with Zollinger-Ellison syndrome inquires as to the cause of his disease. As his physician, you explain that which of the following mechanisms is most likely responsible for the disease?
Destruction of G cells
Destruction of parietal cells
Gastric acid-secreting tumor
Gastrin-secreting tumor
Somatostatin-secreting tumor
Correct answer
Gastrin-secreting tumor
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correct answer: D
In Zollinger-Ellison syndrome, a gastrin-producing tumor is responsible for the excess levels of gastrin. Gastrin, a hormone normally secreted by G cells of the stomach and duodenum, stimulates the secretion of gastric acid by the parietal cells of the stomach.
Characteristic features of the syndrome include recurrent peptic ulcers, diarrhea, weight loss, and abdominal pain. The majority of gastrin-secreting tumors, or gastrinomas, are found in the “gastrinoma triangle,” formed by the cystic duct, junction of the second and third portions of the duodenum, and neck of the pancreas. While 80% of gastrinomas occur sporadically, 20% are associated with MEN I.
Destruction of G cells (Choice A) would lead to a decrease in the production of gastrin. Destruction of parietal cells (Choice B), as occurs in autoimmune gastritis, would result in hypochlorhydria, which, in turn, would cause an elevation in gastrin in an attempt to compensate for the low gastric acid level. Zollinger-Ellison syndrome is the result of a gastrin-secreting tumor, not a gastric acid- secreting tumor. An increase in gastric acid would result in a compensatory decrease in gastrin. Since somatostatin inhibits the release of gastrin, a somatostatin-secreting tumor (Choice E) would result in a decrease in the amount of circulating gastrin.