Adrenal drugs: metyrapone test: practice question

A Pharmacology 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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Pharmacology · Adrenal drugs: metyrapone test

Sample item

A woman who took prednisolone for two years has it stopped, and her hypothalamic-pituitary-adrenal axis is assessed with metyrapone. Plasma cortisol falls as expected, but 11-deoxycortisol and ACTH fail to rise. What is the interpretation?

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

The answer and the reasoning

B. Inadequate pituitary ACTH reserve with a suppressed hypothalamic-pituitary axis

Metyrapone inhibits 11-beta-hydroxylase, blocking the last step of cortisol synthesis. In a normal axis, the fall in cortisol removes negative feedback, ACTH rises and 11-deoxycortisol accumulates. Failure of this rise indicates that the pituitary cannot respond, as after long-term glucocorticoid suppression.

Option by option

  • A. Ectopic ACTH secretion

    Ectopic ACTH secretion would raise ACTH independently of cortisol, which is not seen here.

  • B. Inadequate pituitary ACTH reserve with a suppressed hypothalamic-pituitary axis (correct)

    Lack of an ACTH and 11-deoxycortisol response shows impaired pituitary-adrenal reserve.

  • C. Normal axis, because cortisol fell

    In a normal axis the removal of feedback would raise ACTH and 11-deoxycortisol, not leave them flat.

  • D. Primary adrenal hyperplasia with 11-beta-hydroxylase deficiency

    In 11-beta-hydroxylase deficiency 11-deoxycortisol is already high at baseline, which is not seen here.

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 Pharmacology question

What is the answer to this Pharmacology question?

The best answer is B, Inadequate pituitary ACTH reserve with a suppressed hypothalamic-pituitary axis. Metyrapone inhibits 11-beta-hydroxylase, blocking the last step of cortisol synthesis.

Why is "Ectopic ACTH secretion" not the answer?

Ectopic ACTH secretion would raise ACTH independently of cortisol, which is not seen here.

Why is "Normal axis, because cortisol fell" not the answer?

In a normal axis the removal of feedback would raise ACTH and 11-deoxycortisol, not leave them flat.

Why is "Primary adrenal hyperplasia with 11-beta-hydroxylase deficiency" not the answer?

In 11-beta-hydroxylase deficiency 11-deoxycortisol is already high at baseline, which is not seen here.

What concept does this question test?

It tests Adrenal drugs: metyrapone test in Pharmacology. In a normal axis, the fall in cortisol removes negative feedback, ACTH rises and 11-deoxycortisol accumulates. Failure of this rise indicates that the pituitary cannot respond, as after long-term glucocorticoid suppression.

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 Adrenal drugs: metyrapone test?

Learn drugs as classes, then the exception in each class that an examiner would pick. Then use the flashcards and the other Pharmacology 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.