Endocrinology and diabetes: Nelson 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 and diabetes: Nelson syndrome

Sample item

A woman who had bilateral adrenalectomy for Cushing disease three years ago now has progressive darkening of the skin and a bitemporal visual field defect. Her ACTH is very high. What is the mechanism?

AEnlargement of the ACTH-secreting pituitary adenoma after loss of cortisol feedbackBUnder-replacement of glucocorticoids causing adrenal insufficiencyCEctopic ACTH secretion from a small cell lung carcinomaDRegrowth of residual adrenal tissue secreting cortisol

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

The answer and the reasoning

A. Enlargement of the ACTH-secreting pituitary adenoma after loss of cortisol feedback

In Nelson syndrome, the pituitary corticotroph adenoma enlarges after bilateral adrenalectomy removes cortisol feedback. It causes high ACTH, hyperpigmentation and mass effects such as visual field loss. Pituitary surgery or radiotherapy is used.

Option by option

A. Enlargement of the ACTH-secreting pituitary adenoma after loss of cortisol feedback (correct)
Correct. Loss of negative feedback allows the corticotroph tumour to grow and secrete ACTH.
B. Under-replacement of glucocorticoids causing adrenal insufficiency
Under-replacement raises ACTH and pigments the skin, but does not produce a mass causing visual field loss.
C. Ectopic ACTH secretion from a small cell lung carcinoma
Ectopic ACTH syndrome would cause rapid Cushingoid features rather than a pituitary mass after adrenalectomy.
D. Regrowth of residual adrenal tissue secreting cortisol
Residual adrenal tissue would cause persistent hypercortisolism, not skin darkening with high ACTH.

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, Enlargement of the ACTH-secreting pituitary adenoma after loss of cortisol feedback. In Nelson syndrome, the pituitary corticotroph adenoma enlarges after bilateral adrenalectomy removes cortisol feedback.

Why is "Under-replacement of glucocorticoids causing adrenal insufficiency" not the answer?

Under-replacement raises ACTH and pigments the skin, but does not produce a mass causing visual field loss.

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

Ectopic ACTH syndrome would cause rapid Cushingoid features rather than a pituitary mass after adrenalectomy.

Why is "Regrowth of residual adrenal tissue secreting cortisol" not the answer?

Residual adrenal tissue would cause persistent hypercortisolism, not skin darkening with high ACTH.

What concept does this question test?

It tests Endocrinology and diabetes: Nelson syndrome in General Medicine. It causes high ACTH, hyperpigmentation and mass effects such as visual field loss. Pituitary surgery or radiotherapy is used.

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 Endocrinology and diabetes: Nelson 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.