Glucagon test for insulinoma: a chemical study in 25 cases.

The capillary blood glucose response to lmg of intramuscular glucagon was determined in 13 patients with insulinoma and in 33 normal controls; the insulinoma patients showed a normal initial rise, but this was followed by an abnormally large fall, reaching hypoglycaemic levels between 90 and 180 minutes in every case. In 14 insulinoma patients the response of venous blood glucose and also plasma insulin to lmg of intravenous glucagon was compared with 10 normal controls; there was an abnormally large rise of plasma insulin in 10 of the 14 patients, and in the majority the venous blood glucose was below normal throughout the test. In these 14 patients the plasma insulin response was also determined after oral and intravenous glucose, after oral leucine, and after intravenous tolbutamide, and the value of these tests in the recognition and differential diagnosis of insulinoma was compared with that of the intravenous glucagon test.