Endocrine pancreas: C-peptide: practice question

A Physiology question in the style of the NEET PG paper. Answer it first, then read why the right option is right and why each of the others is wrong.

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Physiology · Endocrine pancreas: C-peptide

Sample item

A 33-year-old woman has recurrent unexplained hypoglycaemic episodes. During an episode her plasma glucose is 38 mg/dL with high insulin, low C-peptide and a negative sulfonylurea screen. What is the correct interpretation?

Original practice item, not a recalled exam question. Nothing here is recorded.

The answer and the reasoning

B. Exogenous insulin administration

Endogenous insulin is released from proinsulin in equimolar amounts with C-peptide. High insulin with suppressed C-peptide means the insulin is coming from outside the pancreas, as in factitious use of insulin. An insulinoma or sulfonylurea would raise both insulin and C-peptide.

Option by option

  • A. Sulfonylurea ingestion

    A sulfonylurea would stimulate beta cells and raise C-peptide, and the screen is negative.

  • B. Exogenous insulin administration (correct)

    Correct. High insulin with low C-peptide indicates injected insulin.

  • C. Adrenal insufficiency

    Adrenal insufficiency causes hypoglycaemia with suppressed insulin.

  • D. Insulinoma

    An insulinoma would give raised C-peptide as well as insulin.

Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.

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Questions about this Physiology question

What is the answer to this Physiology question?

The best answer is B, Exogenous insulin administration. Endogenous insulin is released from proinsulin in equimolar amounts with C-peptide.

Why is "Sulfonylurea ingestion" not the answer?

A sulfonylurea would stimulate beta cells and raise C-peptide, and the screen is negative.

Why is "Adrenal insufficiency" not the answer?

Adrenal insufficiency causes hypoglycaemia with suppressed insulin.

Why is "Insulinoma" not the answer?

An insulinoma would give raised C-peptide as well as insulin.

What concept does this question test?

It tests Endocrine pancreas: C-peptide in Physiology. High insulin with suppressed C-peptide means the insulin is coming from outside the pancreas, as in factitious use of insulin. An insulinoma or sulfonylurea would raise both insulin and C-peptide.

How hard is this question?

We tag it as a multi-step question: it asks you to combine more than one idea. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

How should I study Endocrine pancreas: C-peptide?

For each system, sketch the key graph (pressure–volume loop, oxygen dissociation curve, nephron handling) and explain it aloud. Then use the flashcards and the other Physiology questions on this site to test what stuck.

Is this a real NEET PG question?

No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.