Endocrinology and diabetes: stalk effect hyperprolactinaemia: 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: stalk effect hyperprolactinaemia

Sample item

A 35-year-old woman has headache, bitemporal hemianopia and amenorrhoea. MRI shows a 3 cm sellar mass. Serum prolactin is 85 ng/mL and does not change when the assay is repeated on diluted serum. Other pituitary hormones are low. Which explanation best fits?

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

The answer and the reasoning

D. Stalk compression removing dopamine inhibition of lactotrophs

A large non-functioning macroadenoma can compress the pituitary stalk and block dopamine reaching lactotrophs, causing only a modest prolactin rise. A prolactinoma this large would give levels in the hundreds or thousands. Unchanged results on dilution exclude the hook effect.

Option by option

  • A. Ectopic prolactin secretion by a bronchial tumour

    Ectopic secretion is rare and would not explain the sellar mass.

  • B. Assay artefact caused by extremely high prolactin concentrations

    The hook effect gives falsely low values that rise on dilution, which did not happen.

  • C. Autonomous prolactin hypersecretion by a large lactotroph tumour

    A tumour of this size secreting prolactin would give a much higher level.

  • D. Stalk compression removing dopamine inhibition of lactotrophs (correct)

    Correct. Modest hyperprolactinaemia with a large mass and hypopituitarism is the stalk effect.

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 General Medicine question

What is the answer to this General Medicine question?

The best answer is D, Stalk compression removing dopamine inhibition of lactotrophs. A large non-functioning macroadenoma can compress the pituitary stalk and block dopamine reaching lactotrophs, causing only a modest prolactin rise.

Why is "Ectopic prolactin secretion by a bronchial tumour" not the answer?

Ectopic secretion is rare and would not explain the sellar mass.

Why is "Assay artefact caused by extremely high prolactin concentrations" not the answer?

The hook effect gives falsely low values that rise on dilution, which did not happen.

Why is "Autonomous prolactin hypersecretion by a large lactotroph tumour" not the answer?

A tumour of this size secreting prolactin would give a much higher level.

What concept does this question test?

It tests Endocrinology and diabetes: stalk effect hyperprolactinaemia in General Medicine. A prolactinoma this large would give levels in the hundreds or thousands. Unchanged results on dilution exclude the hook effect.

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 and diabetes: stalk effect hyperprolactinaemia?

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.