Metabolic bone disease: PTH action on bone: practice question

A Orthopaedics 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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Orthopaedics · Metabolic bone disease: PTH action on bone

Sample item

Parathyroid hormone increases bone resorption even though osteoclasts do not have PTH receptors in significant numbers. How does it act?

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

The answer and the reasoning

B. Osteoblasts are stimulated to express RANKL

PTH acts on osteoblast lineage cells, which increase RANKL and reduce osteoprotegerin, so osteoclast formation and activity rise. This explains the bone loss in continuous PTH excess, while intermittent exposure is anabolic.

Option by option

  • A. Osteoclasts are directly inhibited by it

    Direct inhibition of osteoclasts is not the action of PTH.

  • B. Osteoblasts are stimulated to express RANKL (correct)

    Correct. PTH works through osteoblasts, which increase RANKL expression.

  • C. It increases the production of osteoprotegerin

    PTH lowers osteoprotegerin production and does not raise it.

  • D. Osteoclasts take up PTH and are activated

    Osteoclasts have few PTH receptors, so they do not respond directly.

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 Orthopaedics question

What is the answer to this Orthopaedics question?

The best answer is B, Osteoblasts are stimulated to express RANKL. PTH acts on osteoblast lineage cells, which increase RANKL and reduce osteoprotegerin, so osteoclast formation and activity rise.

Why is "Osteoclasts are directly inhibited by it" not the answer?

Direct inhibition of osteoclasts is not the action of PTH.

Why is "It increases the production of osteoprotegerin" not the answer?

PTH lowers osteoprotegerin production and does not raise it.

Why is "Osteoclasts take up PTH and are activated" not the answer?

Osteoclasts have few PTH receptors, so they do not respond directly.

What concept does this question test?

It tests Metabolic bone disease: PTH action on bone in Orthopaedics. This explains the bone loss in continuous PTH excess, while intermittent exposure is anabolic.

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 Metabolic bone disease: PTH action on bone?

Pair each fracture with its classic complication and nerve injured. Then use the flashcards and the other Orthopaedics 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.