[C-peptide: secretion and metabolism in different functional states and with abnormal B-cell function (author's...

Fasting C-peptide levels and those after tolbutamide or glucose stimulation were measured in normal subjects. In patients with various hypo- or hyper-functions of the endocrine pancreas, C-peptide levels were compared with the corresponding insulin levels. In insulin-dependent maturity-onset diabetics there were both normal and elevated serum C-peptide levels. In juvenile diabetics and patients with total duodenopancreatectomy there was no measureable C-peptide. It is concluded that the half-life of C-peptide is three times that of insulin.