Table notes: (1) increased insulin of the "metabolic syndrome (MetS)" (the C-peptide elevation possibly helping to identify the polycystic ovaries associated with this MetS from real PCOS...which probably does not have increased C-peptide unless patient also has MetS), insulinoma (pancreatic or extra-pancreatic), pancreatic beta cell disorder, islet cell hyperplasia, non-insulinoma pancreatogenous hyperinsulinism. (2)antibodies not often generated against the newer recombinant insulin and take around 4 weeks to generate against the older animal-derived insulin.(3) during the processing of proinsulin to insulin in the beta cell of the pancreas, the 31 amino acid connecting peptide which connects the A and B chains, called C-peptide, is enzymatically removed and secreted into the portal vein. C-peptide level decreases with decreasing beta cell secretory reserve. C-peptide circulates independently from insulin and is mainly secreted by the kidneys...levels are elevated in renal failure (4). Exogenous, factitious insulin OD will not have elevated C-peptide levels & endogenous hyperinsulinism will have elevated C-peptide levels.