Decrease in thoracic vertebral bone attenuation with calcium-based phosphate binders in hemodialysis

Area of Science:

• Nephrology
• Bone Metabolism
• Mineral Metabolism

Background:

• Hyperphosphatemia in chronic kidney disease is linked to poor outcomes, including bone disease and mortality.
• Calcium-based phosphate binders are used to manage hyperphosphatemia and secondary hyperparathyroidism.
• A common assumption is that calcium binders benefit bone health in hemodialysis patients.

Purpose of the Study:

• To investigate the comparative effects of calcium-based phosphate binders and sevelamer on bone turnover and vertebral bone attenuation in hemodialysis patients.
• To analyze post hoc data from a randomized trial assessing mineral metabolism and vascular calcification.

Main Methods:

• Post hoc analysis of a 52-week randomized trial in adult hemodialysis patients.
• Comparison of calcium-based phosphate binders versus sevelamer.
• Evaluation of thoracic vertebral bone attenuation using CT scans and markers of bone turnover.

Main Results:

• Calcium-treated patients showed significantly reduced trabecular bone attenuation (p=0.01) and a trend toward reduced cortical bone attenuation.
• Higher serum calcium concentrations were observed in the calcium group, with lower parathyroid hormone (PTH) levels and reduced alkaline phosphatase.
• Over 30% of calcium-treated subjects experienced a significant decrease in bone attenuation.

Conclusions:

• Calcium salts, when used for hyperphosphatemia, may paradoxically decrease bone mineral density in hemodialysis patients.
• Sevelamer treatment was associated with higher levels of bone turnover markers (alkaline phosphatase, osteocalcin, PTH).
• Findings challenge the presumed beneficial effect of calcium on bone in this patient population.