Serum C-peptide in renal failure patients following stimulation of pancreatic secretion.

We have demonstrated persistently elevated serum C-peptide concentrations in patients with chronic renal failure on chronic hemodialysis. A blunted serum C-peptide response to intravenous glucose, glucagon and tolbutamide was also found. However, the response to oral glucose stimulation was greater and more prolonged than in control subjects, probably related to the magnitude of hyperglycemia found in patients with chronic renal failure. These observations suggest the existence of a defect in the renal clearance of C-peptide although an abnormality in C-peptide secretion cannot be excluded.