Review Question - QID 106480

This patient is presenting with severe hypoglycemia likely secondary to exogenous administration of insulin.

C-peptide is the portion of pro-insulin that is cleaved away within the pancreatic beta cell. In normal physiology, c-peptide is present within the circulation in equimolar concentrations with insulin. With the exogenous use of insulin, additional c-peptide is not present within the circulation. This scenario of hypoglycemia often occurs in individuals failing to administer insulin correctly or in healthcare workers wishing to harm themselves. An insulin producing tumor should also be on the differential diagnosis for these patients.

Patel and Macerollo review the diagnosis of diabetes mellitus. They state that in addition to identifying exogenous insulin administration, a c-peptide level can be used as a marker for pancreatic beta-cell function.

Winston reviews 4 cases of suicide presumably by exogenous administration of high doses of insulin. One case was diagnosed with a vitreous insulin level with the other diagnosis was made by elevated levels of insulin in the serum with decreased c-peptide levels. Proper collection and storage of post-mortem specimens is needed.

Illustration A is a schematic displaying the presence of the c-peptide within pro-insulin.

Incorrect Answers:
Answer 1: Genetic testing would be required if an insulinoma was present.
Answer 3: This test is used to diagnose adrenal insufficiency.
Answer 4: This test is used for the diagnosis of diabetes mellitus.
Answer 5: This test is used for the diagnosis of pheochromocytoma.