Gastrin is a peptide normally produced by G cells of the mucosa of the gastric antrum. It is released by direct contact of protein digests of food with the antral mucosa or by mechanical distention of the antrum. The major action of gastrin is to
increase and pepsin output by the parietal and chief cells of the funcdic mucosa. Gastrin also increases gastric mucosal blood flow and has important trophic effects on the mucosa of the stomach. In patients with Zolliger-Ellison syndrome,
gastrin-producing tumors (gastrinomas) release excessive amounts of gastrin, which cause hypersecretion of gastric acid and often severe peptic ulcer disease. Gastrin stimulation tests are frequently necessary in patients with moderately elevated
serum
gastrin levels to differentiate other hyperchlorhydric hypergastrinemic states. The majority of gastrinomas are intrapancreatic, but they also occur in the wall of the duodenum and in parapancreatic lymph nodes. The symptoms of ZES are the same
as
those
of peptic-ulcer disease and result from gastric hyperacidity. Until recently, most deaths of patients with ZES were caused by complications of peptic-ulcer disease. The presently available H2 receptor antagonists effectively control hyperacidity,
however, and peptic-ulcer disease is no longer a major problem. When malignant, about 60% of them, gastrinomas are usually slow growing, but they do metastasize and can cause death in some patients So the aim of the therapy for ZES is focused on
resection of the gastrinoma. If tumour resection is complete, gastric acid secretion, basal and secretin-stimulated serum gastrin levels usually return to normal in most patients with ZES but not all cases. When metastatic gastrinoma is found
especially
in the liver, the 5-year survival rate is only 20%. Gastrinoma and ZES occur in 50~60% of patients with MEN 1 syndrom. In that case, they are less likely to be malignant in MEN I patient.
|