C-peptide

C-peptide

the central connecting polypeptide which is part of the proinsulin molecule. It is released when the two chains of insulin are cleaved off of the single chain looped polypeptide of proinsulin.

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C-peptide

Connecting peptide Endocrinology A biologically inactive moiety of proinsulin produced endogenously in the pancreas, and stored in secretory granules in a 1:1 ratio with insulin; unlike factitious hypoglycemia, which is induced by insulin of exogenous origin, an ↑ in C-peptide–≥
0.2 nmol/L, as well as ↑ insulin, ≥ 42 pmol/L is characteristic of insulinoma; C-peptide quantification is used to detect fictitious insulin injection and diagnose insulin-secreting tumors in diabetics, where > 7 ng/ml of C-peptide after induced hypoglycemia supports a diagnosis of insulinoma. See Diabetes, Insulin.