C-peptide is the "connecting" peptide released from proinsulin after its cleavage in the pancreatic beta-cell. The increase in C-peptide following intravenous injection of glucagon has been used as a measure of residual pancreatic beta-cell function in diabetics. Patients with little or no increase following stimulation have little if any beta-cell function and require insulin for glucose homeostasis. Diabetic patients with sufficient response to stimulation may show adequate glycemic control without the need for exogenous insulin.
