Basal insulin secretion increases with the onset of non-insulin dependent diabetes

Seven out of 206 subjects investigated at 6-mth intervals with a glucose tolerance test developed non-insulin dependent diabetes. The mean fasting serum C-peptide concentration in the diabetic subjects was greater at the time of diagnosis of diabetes than 6 mth prior to diagnosis (1.25 and 1.01 nmol/l respectively, p less than 0.05). There was no significant difference in mean ideal body weight and maximum post-glucose serum C-peptide reactivity (CPR) before and at diagnosis. There was no change in mean fasting CPR during a similar 6 mth period (0.84 and 0.84 nmol/l respectively) in 17 subjects with normal glucose tolerance matched with the diabetics for age and ideal body weight. It is postulated that at least in some subjects the transition to diabetes is accompanied by an increase in insulin resistance.