C-peptide in diabetes mellitus treated with insulin. A 3-year epidemiological study on the island of Falster, Denmark.

In a 3 yr prospective epidemiological study of 227 insulin-treated diabetics the clinical value of fasting C-peptide measurements for discriminating between insulin dependence and non-insulin dependence was assessed. A significant difference (p less than 0.01) in fasting C-peptide secretion was found between diabetics with an early onset age (less than 30 yr) and a late onset age (greater than or equal to 30 yr). Among diabetics with a late onset age (n = 124) 45% were classified as non-insulin dependent according to fasting C-peptide levels (greater than 0.40 pmol/ml) and characterized by overweight. Diabetics with C-peptide concentrations less than 20 pmol/ml were characterized by an early onset of diabetes mellitus (less than 30 yr), the duration of diabetes mellitus (greater than 5 yr), slight deviation from ideal weight, development of insulin antibodies and high daily insulin dosage. Among the 57 diabetics with a C-peptide level greater than 0.40 pmol/ml 31 accepted and could maintain good metabolic control in a period of 3 yr after change from treatment with insulin to treatment with oral hypoglycaemic agent and diet or diet regime alone. It is concluded that measurement of fasting C-peptide is of additional clinical importance for the choice of treatment of diabetics.