Changes in glucose tolerance and insulin response in subclinical diabetes after treatment

In this study, 121 patients who showed diabetic or decreased glucose tolerance and were treated with diet alone for one to fifteen years were investigated as subclinical diabetes. Glucose tolerance in these patients was improved or remained unchanged during the clinical course. Aggravation in glucose tolerance was observed in only seven cases. However, abnormalities in glucose tolerance were still found in 107 cases (88%) of the subclinical diabetes. Insulin response to oral glucose was investigated in 74 patients with subclinical diabetes. Delayed response and/or decreased response in the initial phase were demonstrated in 58 out of 74 patients (79%). No significant difference was observed in the insulinogenic index (ratio of insulin increment/glucose increment) at 30 min between the normal controls and either group with abnormal glucose tolerance. Diabetic retinopathy, including microaneurysm, was detected in 25 out of 109 patients with diabetic glucose tolerance. Abnormal insulin response, delayed and/or decreased, was demonstrated in 13 of 16 patients with diabetic retinopathy (81%). These results indicate the possibility that subclinical diabetes in the present study is a mild type of primary diabetes. In addition, it is suggested that abnormal response of plasma insulin to glucose, delayed and/or decreased, might be one of the prominent findings in diagnosis of diabetes mellitus.