Metabolic bone disease: osteoprotegerin: 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: osteoprotegerin

Sample item

Osteoblasts and stromal cells release a soluble protein that acts as a decoy receptor for RANKL, so that osteoclast formation is limited. What is it?

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

The answer and the reasoning

B. Osteoprotegerin

RANKL on osteoblast lineage cells binds RANK on osteoclast precursors to drive differentiation. Osteoprotegerin binds RANKL first and prevents this, so the RANKL to OPG ratio determines bone resorption.

Option by option

  • A. Calcitonin

    Calcitonin is a thyroid hormone that acts directly on osteoclast receptors.

  • B. Osteoprotegerin (correct)

    Correct. Osteoprotegerin is the decoy receptor that binds RANKL.

  • C. Osteocalcin

    Osteocalcin is an osteoblast protein used as a marker of bone formation.

  • D. Sclerostin

    Sclerostin inhibits Wnt signalling and bone formation and does not bind RANKL.

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, Osteoprotegerin. RANKL on osteoblast lineage cells binds RANK on osteoclast precursors to drive differentiation.

Why is "Calcitonin" not the answer?

Calcitonin is a thyroid hormone that acts directly on osteoclast receptors.

Why is "Osteocalcin" not the answer?

Osteocalcin is an osteoblast protein used as a marker of bone formation.

Why is "Sclerostin" not the answer?

Sclerostin inhibits Wnt signalling and bone formation and does not bind RANKL.

What concept does this question test?

It tests Metabolic bone disease: osteoprotegerin in Orthopaedics. Osteoprotegerin binds RANKL first and prevents this, so the RANKL to OPG ratio determines bone resorption.

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: osteoprotegerin?

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.