In fracture healing, which growth factor is primarily responsible for the transition from soft to hard callus by promoting chondrocyte hypertrophy and endochondral ossification?
- A Indian Hedgehog (IHH) ✓
- B BMP-2
- C PDGF
- D TGF-β1
Correct answer: A. Indian Hedgehog (IHH)
Explanation
Indian Hedgehog (IHH) is a key regulator in endochondral ossification during fracture healing; it is secreted by hypertrophic chondrocytes and promotes chondrocyte maturation, vascular invasion, and conversion of cartilaginous (soft) callus to woven bone (hard callus). BMP-2 is important for osteoprogenitor differentiation and cartilage induction. PDGF promotes cell proliferation. TGF-β1 regulates early inflammation and matrix production but is not the primary driver of this specific transition.
Reference: Maheshwari Essential Orthopaedics, 6th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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