To the Editor.—
The authors of "Reactive Hypoglycemia" (243:1151, 1980) state that "hypoglycemic symptoms occurring during the [oral glucose tolerance] test were not related to level of plasma glucose nadir or to rate of descent of glucose level." Our recently published results1 support the conclusion that the blood glucose nadir should not be used as the sole criterion for diagnosis.However, the hypoglycemic index2 (defined as the fall in blood glucose level during a 90-minute period before reaching the nadir divided by the value of the glucose nadir) can separate with no overlap symptomatic from asymptomatic patients. The hypoglycemic index correlated with the insulin levels 90 minutes before the lower blood glucose levels. Therefore, an elevated hypoglycemic index is associated with symptoms and reflects later hyperinsulinism.