Endocrinology: Cushing syndrome: practice question

A General Medicine 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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General Medicine · Endocrinology: Cushing syndrome

Sample item

A woman has features of Cushing syndrome. Morning ACTH is raised, and serum cortisol is not suppressed by low-dose dexamethasone but falls by more than 50% after high-dose dexamethasone. What is the likely source?

AA pituitary corticotroph adenoma (Cushing disease)BExogenous glucocorticoid useCAn adrenal adenomaDEctopic ACTH secretion from a small cell lung cancer

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

The answer and the reasoning

A. A pituitary corticotroph adenoma (Cushing disease)

A raised ACTH points to ACTH-dependent Cushing syndrome. Pituitary adenomas retain partial sensitivity to feedback and suppress with high-dose dexamethasone, while most ectopic ACTH sources do not. Adrenal tumours and exogenous steroids cause low ACTH. Inferior petrosal sinus sampling and pituitary MRI help to confirm.

Option by option

A. A pituitary corticotroph adenoma (Cushing disease) (correct)
Correct. ACTH-dependent disease with high-dose suppression is typical of Cushing disease.
B. Exogenous glucocorticoid use
Exogenous steroids suppress ACTH and cause low cortisol on testing.
C. An adrenal adenoma
An adrenal adenoma produces cortisol autonomously and suppresses ACTH, which would be low.
D. Ectopic ACTH secretion from a small cell lung cancer
Ectopic ACTH is usually not suppressed by high-dose dexamethasone.

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.

Questions about this General Medicine question

What is the answer to this General Medicine question?

The best answer is A, A pituitary corticotroph adenoma (Cushing disease). A raised ACTH points to ACTH-dependent Cushing syndrome.

Why is "Exogenous glucocorticoid use" not the answer?

Exogenous steroids suppress ACTH and cause low cortisol on testing.

Why is "An adrenal adenoma" not the answer?

An adrenal adenoma produces cortisol autonomously and suppresses ACTH, which would be low.

Why is "Ectopic ACTH secretion from a small cell lung cancer" not the answer?

Ectopic ACTH is usually not suppressed by high-dose dexamethasone.

What concept does this question test?

It tests Endocrinology: Cushing syndrome in General Medicine. Pituitary adenomas retain partial sensitivity to feedback and suppress with high-dose dexamethasone, while most ectopic ACTH sources do not. Adrenal tumours and exogenous steroids cause low ACTH. Inferior petrosal sinus sampling and pituitary MRI help to confirm.

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 Endocrinology: Cushing syndrome?

For each disease know the classic presentation, the best test, and the first-line treatment. Then use the flashcards and the other General Medicine 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.