Question

A patient presents with symptoms of hypoglycemia. Investigations reveal decreased blood glucose and increased insulin levels. A C-peptide assay shows a normal level of C-peptide. The most likely diagnosis is:

• A. Insulinoma
• B. Accidental sulfonylurea ingestion
• C. Accidental exogenous insulin administration
• D. Accidental metformin ingestion

Hint:

Outside insulin has no C-peptide, so insulin is high but C-peptide is not.

Answer 1

The Correct Option is C

Step 1: The key tool here is C-peptide. The pancreas makes proinsulin, which is split into one insulin molecule and one C-peptide molecule. So insulin made inside the body always comes with matching C-peptide.

Step 2: Insulin injected from outside (a pharmaceutical product) contains no C-peptide. So when someone takes external insulin, blood insulin rises while C-peptide is suppressed by the feedback shutdown of the pancreas. High insulin with low or non-elevated C-peptide points to exogenous insulin.

Step 3: The stem gives hypoglycemia, high insulin, and a C-peptide that is not raised. This pattern fits exogenous insulin administration. So option C is the best answer, matching the printed key.

Step 4: Why not the others. In insulinoma the tumour secretes endogenous insulin, so C-peptide would be high, not in line with the stem, so A is wrong. Sulfonylureas push the pancreas to release its own insulin, so both insulin and C-peptide would be high, so B is wrong. Metformin does not raise insulin and does not usually cause hypoglycemia on its own, so D is wrong.

Correct option: C.