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 nurse has recurrent fasting hypoglycaemia with high serum insulin, low C-peptide and negative sulfonylurea screen. What is the cause?

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

The answer and the reasoning

C. Surreptitious injection of exogenous insulin

Proinsulin is cleaved into insulin and C-peptide in equimolar amounts. Exogenous insulin raises insulin but suppresses endogenous secretion, so C-peptide is low. Insulinoma and sulfonylureas raise both, with the screen being positive for the drug.

Option by option

  • A. Adrenal insufficiency

    Adrenal insufficiency would be associated with low insulin and a different clinical picture.

  • B. An insulin-secreting pancreatic beta-cell tumour

    An insulinoma produces high C-peptide along with insulin.

  • C. Surreptitious injection of exogenous insulin (correct)

    Correct. High insulin with suppressed C-peptide indicates an external source.

  • D. Ingestion of a sulfonylurea

    Sulfonylurea use raises C-peptide and the drug screen would be positive.

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 C, Surreptitious injection of exogenous insulin. Proinsulin is cleaved into insulin and C-peptide in equimolar amounts.

Why is "Adrenal insufficiency" not the answer?

Adrenal insufficiency would be associated with low insulin and a different clinical picture.

Why is "An insulin-secreting pancreatic beta-cell tumour" not the answer?

An insulinoma produces high C-peptide along with insulin.

Why is "Ingestion of a sulfonylurea" not the answer?

Sulfonylurea use raises C-peptide and the drug screen would be positive.

What concept does this question test?

It tests Endocrine pancreas: C-peptide in Physiology. Exogenous insulin raises insulin but suppresses endogenous secretion, so C-peptide is low. Insulinoma and sulfonylureas raise both, with the screen being positive for the drug.

How hard is this question?

We tag it as an application question: it asks you to use a fact on a patient or a finding. 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.