Current approaches to measurement of insulin secretion.

The studies reviewed in this article have indicated that C-peptide and insulin are cosecreted from the beta cell in equimolar concentration, that C-peptide does not undergo significant hepatic extraction, and that its MCR remains constant over the physiologic range of concentrations. Furthermore, the peripheral kinetics of distribution of C-peptide can be described by a two-compartment mathematical model. If model parameters are derived in individual subjects by analysis of C-peptide decay curves, this information can subsequently be used to derive insulin secretion rates with a great degree of accuracy from endogenously secreted C-peptide concentrations. The application of this approach to clinical research studies should greatly enhance our understanding of insulin secretion.