In suspected Paget's disease, which laboratory test is most informative?

• A. Alkaline Phosphatase
• B. Calcium
• C. Sodium
• D. Phosphate

Answer: (A)

Paget disease causes a marked increase in bone turnover, with osteoblasts working overtime to lay down new bone after rapid resorption. Alkaline phosphatase is produced by active osteoblasts, so its level rises proportionally with bone formation and turnover. This makes alkaline phosphatase the most sensitive and informative single lab marker for suspected Paget disease and for tracking disease activity or response to therapy. Calcium and phosphate generally stay normal because systemic calcium balance isn’t driven by the localized abnormal bone remodeling in Paget’s, and sodium isn’t tied to bone turnover. So this test best reflects the ongoing process in Paget disease among the options provided.