Diagnostic value of sodium tolbutamide test in hypoglycemia.

The intravenous Na-tolbutamide test was done on various types of hypoglyce mia and the following conclusions were obtained: (1) Though very useful in the screening of hypoglycemia, the test is not always satisfactory for the differential diagnosis of various types of hypoglycemia. (2) The diagnosis of hypoglycemia by means of the Na-tolbutamide test is con sidered practically established when the recovering ability from hypoglycemic levels is absent or insufficient, so as to give a value of the recovery index mostly 0.5 or less, and the stationary value is not higher than 55 mg/100 ml. (3) Pronounced hypoglycemia occasionally persists in some cases of functional hypoglycemia. Temporary rise in the blood sugar levels is observed in some cases of pancreatic hyperinsulinism. Differential diagnosis between the two types of hypoglycemia is impossible when only the Na-tolbutamide test is employed. (4) In a patient with diabetes complicated with hypoglycemia, the blood sugar level 20 and 30 minutes after intravenous tolbutamide injection showed an obvious decrease in the decline rate. (5) Biphasic fluctuations of blood sugar levels after intravenous tolbutamide injection were observed in three cases of hyperinsulinism.