Question

Factors that inhibit osteoclasts are:
(A). Calcitonin
(B). PGE2
(C). TNF
(D). TGF beta
Choose the correct answer from the options given below:

• A. (A), (B) and (C) only.
• B. (A), (B) and (D) only.
• C. (A), (B), (C) and (D).
• D. (B), (C) and (D) only.

Hint:

Calcitonin is the most potent and direct physiological inhibitor of osteoclasts.
Inflammatory cytokines like TNF almost always stimulate osteoclast activity and accelerate bone loss.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Osteoclasts are specialized multinucleated cells responsible for bone resorption.
Their activity is tightly regulated by a balance of stimulating and inhibiting systemic hormones, cytokines, and growth factors.

Step 2: Detailed Explanation:
- Calcitonin (A): A hormone secreted by the thyroid gland that directly binds to receptors on osteoclasts, causing rapid inhibition of bone resorption.
- TGF-beta (D): A growth factor stored in the bone matrix that acts to inhibit osteoclast differentiation and activity while promoting osteoblast function.
- PGE2 (B): Prostaglandin E2 generally stimulates osteoclastic bone resorption but can exhibit complex dual regulatory behavior, sometimes exerting inhibitory effects at high concentrations.
- TNF (C): Tumor Necrosis Factor is a well-known inflammatory cytokine that strongly stimulates osteoclastogenesis and bone resorption.
Therefore, among the provided options, the group containing the most significant osteoclast inhibitors is (A), (B), and (D).

Step 3: Final Answer:
The correct option is (B).