Use of calcium provocative test in the diagnosis of gastroenteropancreatic endocrine tumors.

Calcium infusion has been advocated as a provocative test for the diagnosis of some endocrine tumors of the pancreas and gastrointestinal tract (gastrinoma, insulinoma, intestinal carcinoids). The release of gastrin from gastrinoma tissue is very sensitive to alterations in the serum calcium level, and the calcium infusion test is recommended in Zollinger-Ellison syndrome when the results of secretin stimulation are equivocal. The calcium provocative test in the detection of insulinoma and carcinoid tumors is less reliable than other safer and simpler procedures. Intravenous injection of calcium followed by pentagastrin stimulates the release of somatostatin in patients with somatostatinoma and offers a reliable means for establishing the diagnosis of this tumor. Calcium administration has not proven to be useful in the diagnosis of other endocrine tumors of the digestive system.