[The clinical value of C-peptide assay (author's transl)].

The C-peptide is a polypeptide generated from enzymatic cleavage of proinsulin into insulin in pancreatic B. cell. C-peptide and insulin are secreted in an equimolar ratio. For this reason. C-peptide radio-immunoassay in blood or urine reflects the insulin secretion when direct insulin determination cannot be done (insulin treatment, circulating insulin antibodies). This assay is mainly used in clinical and investigational studies of insulin dependent diabets. It enabled demonstation of residual secretion of insulin in numerous insulin dependent patients (70% during the first year and 15% after the 15th year of the disease). Persistence of insulin secretion may play a role in the natural history of diabetes since patients with detectable C-peptide immunoreactivity have more stable diabetes, are controlled by lower insulin dose and are less ketosis prone than the others. Factors which influence persistence of B. cell activity in some IDD remain unknown.