On the diversity of insulin secretion and sensitivity in subjects with impaired glucose tolerance

Insulin secretion and sensitivity are basic characteristics determining the glucose tolerance. The aim of this study was to investigate if derangements in these two main characteristics were generally found in subjects with impaired glucose tolerance (IGT). The early insulin response at the intravenous glucose tolerance test (IVGTT) in 42 subjects with IGT was found to be correlated to the glucose tolerance (r = -0.38, p < 0.01 vs, fasting glucose and r = 0.35, p < 0.02, vs the k-value of IVGTT) while fasting insulin was found to be closely correlated to insulin sensitivity, measured by the euglycemic clamp method (r = -0.83, p < 0.003, n = 11). Using data obtained at the IVGTT's in the IGT subjects, different patterns of insulin secretion were found representing different combinations of impairments in insulin secretion and sensitivity. However, in the majority of the IGT subjects a marked decrease in the early insulin response and a fasting hyperinsulinemia were found. The present study suggest such a characterization by the IVGTT to be of importance for a better understanding of the dynamic interplay between insulin secretion and sensitivity in IGT subjects.