Clinical biochemistry: hypoglycaemia work-up: practice question

A Biochemistry 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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Biochemistry · Clinical biochemistry: hypoglycaemia work-up

Sample item

A 28-year-old nurse has recurrent symptomatic hypoglycaemia. During an episode, glucose is 38 mg/dL with insulin markedly raised, C-peptide suppressed, beta-hydroxybutyrate low and sulfonylurea screen negative. What is the most likely cause?

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

The answer and the reasoning

A. Exogenous insulin administration

Endogenous insulin secretion is accompanied by equimolar C-peptide, which is released from the cleaved proinsulin. High insulin with suppressed C-peptide shows that the insulin came from outside, as with injected insulin. Insulinoma and sulfonylureas both give high insulin and high C-peptide, the latter being excluded by a negative screen. Adrenal insufficiency causes hypoglycaemia with low insulin.

Option by option

  • A. Exogenous insulin administration (correct)

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

  • B. Sulfonylurea ingestion

    Sulfonylurea ingestion would raise C-peptide and the drug screen would be positive.

  • C. Insulinoma

    Insulinoma would produce high C-peptide as well as insulin.

  • D. Adrenal insufficiency

    Adrenal insufficiency would show low insulin and a high ACTH with low cortisol.

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 Biochemistry question

What is the answer to this Biochemistry question?

The best answer is A, Exogenous insulin administration. Endogenous insulin secretion is accompanied by equimolar C-peptide, which is released from the cleaved proinsulin.

Why is "Sulfonylurea ingestion" not the answer?

Sulfonylurea ingestion would raise C-peptide and the drug screen would be positive.

Why is "Insulinoma" not the answer?

Insulinoma would produce high C-peptide as well as insulin.

Why is "Adrenal insufficiency" not the answer?

Adrenal insufficiency would show low insulin and a high ACTH with low cortisol.

What concept does this question test?

It tests Clinical biochemistry: hypoglycaemia work-up in Biochemistry. High insulin with suppressed C-peptide shows that the insulin came from outside, as with injected insulin. Insulinoma and sulfonylureas both give high insulin and high C-peptide, the latter being excluded by a negative screen. Adrenal insufficiency causes hypoglycaemia with low insulin.

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 Clinical biochemistry: hypoglycaemia work-up?

Build one table of enzyme deficiency, disease, inheritance and key finding, then revise it by spaced recall. Then use the flashcards and the other Biochemistry 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.