Plasma insulin response during the 50 g oral glucose tolerance test was determined in three groups classified according to GTT results, i. e. normal, borderline and diabetic group.
Results were obtained as follows.
(1) In the normal group, the plasma insulin rose to maximal value after 30 minutes and then returned to the initial level within 120 minutes. The insulin levels changed in parallel with blood glucose levels.
(2) A low and delayed insulin response was obtained in the diabetic group.
(3) The characteristic findings of the insulin response in the borderline group were: low insulin level at the 30 minutes and high insulin level at 60 minutes and 120 minutes. However, it was revealed that the later high insulin secretion of the borderline group as a whole was due to high insulin levels at 60 and 120 minutes in delayed hyperglycemic subjects. Also the insulin at 120 minutes in subjects with a normal glucose level at 120 minutes was the same as that of the normal group.
(4) The ΔIRI/ΔBS at 30 minutes for each indivisuals was above 0.4 in the normal group except only one case, and it was below 0.4 in the diabetic group. In the borderline group the values of ΔIRI/ΔBS were distributed in a broad range, but they tended to be low in subjects with high peak blood glucose levels.