C-peptide
C-peptide is a single chain, 31 amino-acid-polypeptide that connects the N-terminal of the insulin A-chain and C‑terminal of the insulin B-chain. Equimolar amounts of C-peptide are released together with insulin upon secretion. Due to the almost constant, and in comparsion with insulin, less efficient catabolism of C-peptide in the liver, the determination of C-peptide provides more realistic information about secretion by the b-cells than the determination of insulin itself. The determination of C-peptide can be used as an aid in the diagnosis and monitoring of diabetes or other insulin secretion disorders.