After suffering a seizure, a 23-year old woman is found to have profound hypoglycemia. Determination of which of the following would aid in differentiating exogenous hyperinsulinemia from endogenous hyperinsulinemia?

- Distinguishing endogenous insulin production from exogenous insulin (therapeutically or surreptitiously administered) is done by quantitation of C-peptide. - C-peptide Fragment of proinsulin molecule which split off during synthesis of insulin. Circulating C-peptide is characteristically increased in patients with increased endogenous insulin production. C peptide is not increased in exogenous insulin administration, because it is removed during purification of commercial insulin preparations.