Diagnostic value of intravenous glucagon test in insulinoma

The intravenous glucagon test was performed in 11 patients with insulinoma and the diagnostic significance of the test was studied in comparison with the glucose test, the tolbutamide test and the arginine test. The curves of plasma insulin following the intravenous administration of glucagon were markedly different and strange in those patients with insulinoma compared with the normal controls. The maximal levels of plasma insulin ranged from 85 to 400 muU/ml, exceeding the normal range in 10 out of 11 patients, or 91%. Increased levels in the maximal plasma insulin were observed in 63%, 100% and 56% through the glucose test, the tolbutamide test and the arginine test, respectively. The distribution of the insulin areas, calculated from the insulin curves during these tests, was shown to be similar to that of the maximal levels of plasma insulin. There was no significant correlations between the maximal levels of plasma insulin in the glucagon test and the glucose test, the tolbutamide test or the arginine test. The present experiment demonstrated that the intravenous glucagon test, next to the tolbutamide test, caused a large increase in plasma insulin, and therefore, that this test is one of the most useful tools among the provocation tests, for the diagnosis of insulinoma.