Prevalence of insulin deficiency among initially non-insulin-dependent middle-aged diabetic individuals

The endogenous insulin secretion capacity of 171 insulin-treated middle-aged persons with diabetes (81 men, 90 women) of the Kuopio University Central Hospital district (population 250,000), East Finland, was measured by the C-peptide response to glucagon. The prevalence of insulin deficiency among initially non-insulin-dependent diabetic (NIDDM) individuals was calculated on the basis of those who were initially treated with diet or oral drugs and 3 yr or more after diagnosis had been treated with insulin and were insulin deficient in this study. The prevalence of complete insulin deficiency (postglucagon C-peptide undetectable) was among initially NIDDM individuals of the same region, 0.7% in men and 1.2% in women. Using the postglucagon C-peptide level of 0.20 nmol/L as a cut-off point, the prevalence of insulin deficiency was 2.0% in men and 1.9% in women and, on the basis of C-peptide level of 0.60 nmol/L, the prevalence of insulin deficiency was 3.5% in men and 2.7% in women. Our data suggest that the deterioration of insulin secretion capacity in NIDDM to the level that leads to insulin dependency occurs less often than has been previously suggested.