In Paget's disease (osteitis deformans), the characteristic change in serum biochemistry is:

• A Elevated calcium, low phosphate, and elevated PTH
• B Elevated serum alkaline phosphatase with normal calcium and phosphate ✓
• C Low calcium, elevated phosphate, and elevated alkaline phosphatase
• D Elevated calcium, normal alkaline phosphatase, low PTH

Explanation

Paget's disease involves markedly increased osteoblastic and osteoclastic activity producing structurally abnormal bone. The hallmark biochemical abnormality is markedly elevated serum alkaline phosphatase (ALP) reflecting the intense osteoblastic activity. Calcium and phosphate remain normal (steady-state equilibrium between resorption and formation, though immobilisation can cause hypercalcaemia). Urine hydroxyproline is elevated (osteoclast marker). ALP is also used to monitor response to bisphosphonate therapy. Sarcomatous transformation occurs in 1% and is heralded by a new rise in ALP.

Reference: Maheshwari Essential Orthopaedics, 6th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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