Reproduction: prolactin regulation: practice question

A Physiology 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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Physiology · Reproduction: prolactin regulation

Sample item

A 26-year-old woman taking metoclopramide for nausea develops galactorrhoea and amenorrhoea. Serum prolactin is raised. Why?

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

The answer and the reasoning

A. D2 receptor blockade on lactotrophs removes the tonic dopamine inhibition of prolactin

Prolactin is the only anterior pituitary hormone under predominantly inhibitory hypothalamic control, through dopamine (the prolactin-inhibiting factor) from the tuberoinfundibular neurones. D2 antagonists such as metoclopramide, domperidone and antipsychotics remove this brake. The raised prolactin also suppresses GnRH pulses, causing amenorrhoea.

Option by option

  • A. D2 receptor blockade on lactotrophs removes the tonic dopamine inhibition of prolactin (correct)

    Loss of dopaminergic inhibition lets prolactin rise, with secondary GnRH suppression.

  • B. Metoclopramide stimulates oxytocin release, which in turn raises prolactin

    Oxytocin is involved in milk ejection and is not the cause of the rise in prolactin.

  • C. Metoclopramide lowers oestrogen, which releases prolactin from inhibition

    Oestrogen stimulates rather than inhibits prolactin secretion.

  • D. Metoclopramide stimulates TRH release, which is the main drive for prolactin

    TRH does stimulate prolactin, but metoclopramide does not act by raising TRH.

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 Physiology question

What is the answer to this Physiology question?

The best answer is A, D2 receptor blockade on lactotrophs removes the tonic dopamine inhibition of prolactin. Prolactin is the only anterior pituitary hormone under predominantly inhibitory hypothalamic control, through dopamine (the prolactin-inhibiting factor) from the tuberoinfundibular neurones.

Why is "Metoclopramide stimulates oxytocin release, which in turn raises prol…" not the answer?

Oxytocin is involved in milk ejection and is not the cause of the rise in prolactin.

Why is "Metoclopramide lowers oestrogen, which releases prolactin from inhibi…" not the answer?

Oestrogen stimulates rather than inhibits prolactin secretion.

Why is "Metoclopramide stimulates TRH release, which is the main drive for pr…" not the answer?

TRH does stimulate prolactin, but metoclopramide does not act by raising TRH.

What concept does this question test?

It tests Reproduction: prolactin regulation in Physiology. D2 antagonists such as metoclopramide, domperidone and antipsychotics remove this brake. The raised prolactin also suppresses GnRH pulses, causing amenorrhoea.

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 Reproduction: prolactin regulation?

For each system, sketch the key graph (pressure–volume loop, oxygen dissociation curve, nephron handling) and explain it aloud. Then use the flashcards and the other Physiology 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.