In order to determine whether the symptom of “mild glucose intolerance” is associated with functional β cell abnormalities, differing depending on their etiology, the insulin response to intravenously injected glucose was compared with that to intravenous tolbutamide in three homogeneous groups of subjects. Normal weight (NW) subjects comprised one group; chronic pancreatitis (CP) patients'another and obese subjects (O) the other. Each group included both nondiabetic and chemical diabetic subjects.
A. In nondiabetic subjects the early insulin response to glucose (0-10' post glucose insulin area) was similar to that to tolbutamide (NW:310N/ml. x mn. versus 343-CP:299 versus 318-O:576 versus 600).
B. In all the diabetics the early insulin response to glucose was diminished compared to their nondiabetic counterparts (NW:114 versus 310; CP:120 versus 299; O:320 versus 576.
C. The early response to tolbutamide, compared with that of their nondiabetic counterparts, was similar for the diabetic subjects in the normal-weight (333 to 343 for the controls) and overweight, having or not having a family history of diabetes, (779 and 752 respectively to 600) groups but lower for the diabetics in the chronic pancreatitis group (120 to 318). While in the chemical diabetes of chronic pancreatitis patients the lower response to glucose seems due to a reduction in the functional mass of the cells, in essential diabetes of normal weight as well as obese subjects it is related to an insensitivity of the pancreas to glucose. Estimation of the latter by comparison with the response to tolbutamide in a given individual allows one to dispense with the necessity of referring to a control group and to eliminate the influence of hyperinsulinism.