How does metabolic acidosis influence bone health in CKD?

• A. Promotes bone formation.
• B. Promotes bone resorption to buffer acid, contributing to renal osteodystrophy.
• C. No effect on bones.
• D. Strengthens bone density.

Answer: (B)

Metabolic acidosis in CKD creates an acidic environment that bone works to buffer. Hydrogen ions are neutralized by buffering systems, and bone minerals—calcium and phosphate—are released from the bone matrix to help neutralize the excess acid. This shift toward bone resorption weakens bone structure over time. Acidosis also directly stimulates osteoclast activity and can suppress osteoblast function, tipping the balance toward breakdown. In CKD, phosphate retention and reduced vitamin D activation promote secondary hyperparathyroidism, which further drives bone resorption. The combined effect is renal osteodystrophy, a bone disease characterized by loss of bone density and impaired strength.