Decrease in thoracic vertebral bone attenuation with calcium-based phosphate binders in hemodialysis.
We performed a post hoc analysis of a 52-week randomized trial conducted in adult hemodialysis patients that compared the effects of calcium-based phosphate binders and sevelamer, a nonabsorbable polymer, on parameters of mineral metabolism and vascular calcification by electron beam tomography. In this analysis, we evaluated the relative effects of calcium and sevelamer on thoracic vertebral attenuation by CT and markers of bone turnover. Subjects randomized to calcium salts experienced a significant reduction in trabecular bone attenuation and a trend toward reduction in cortical bone attenuation, in association with higher concentrations of serum calcium, lower concentrations of PTH, and reduced total and bone-specific alkaline phosphatase.


BACKGROUND
In patients with chronic kidney disease, hyperphosphatemia is associated with osteodystrophy, vascular and soft tissue calcification, and mortality. Calcium-based phosphate binders are commonly prescribed to reduce intestinal phosphate absorption and to attenuate secondary hyperparathyroidism. Clinicians and investigators have presumed that, in hemodialysis patients, calcium exerts beneficial effects on bone.


METHODS
We performed a post hoc analysis of a 52-week randomized trial conducted in adult hemodialysis patients that compared the effects of calcium-based phosphate binders and sevelamer, a nonabsorbable polymer, on parameters of mineral metabolism and vascular calcification by electron beam tomography. In this analysis, we evaluated the relative effects of calcium and sevelamer on thoracic vertebral attenuation by CT and markers of bone turnover.


CONCLUSIONS
The average serum phosphorus and calcium x phosphorus products were similar for both groups, although the average serum calcium concentration was significantly higher in the calcium-treated group. Compared with sevelamer-treated subjects, calcium-treated subjects showed a decrease in thoracic vertebral trabecular bone attenuation (p = 0.01) and a trend toward decreased cortical bone attenuation. More than 30% of calcium-treated subjects experienced a 10% or more decrease in trabecular and cortical bone attenuation. On study, sevelamer-treated subjects had higher concentrations of total and bone-specific alkaline phosphatase, osteocalcin, and PTH (p < 0.001). When used to correct hyperphosphatemia, calcium salts lead to a reduction in thoracic trabecular and cortical bone attenuation. Calcium salts may paradoxically decrease BMD in hemodialysis patients.
Raggi
Paolo
P
Tulane University School of Medicine, New Orleans, Louisiana, USA.
James
George
G
Burke
Steven K
SK
Bommer
Jürgen
J
Chasan-Taber
Scott
S
Holzer
Herwig
H
Braun
Johan
J
Chertow
Glenn M
GM
D000368:Aged; D000469:Alkaline Phosphatase / Q000378:metabolism; D001011:Aorta / Q000473:pathology; D015415:Biomarkers / Q000097:blood; D001842:Bone and Bones / Q000378:metabolism; D002118:Calcium / Q000737:chemistry* / Q000378:metabolism; D004583:Electrons; D004852:Epoxy Compounds / Q000494:pharmacology*; D005260:Female; D006801:Humans; D007676:Kidney Failure, Chronic / Q000097:blood* / Q000188:drug therapy; D008159:Lumbar Vertebrae / Q000378:metabolism / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D010281:Parathyroid Hormone / Q000378:metabolism; D028044:Phosphate-Binding Proteins / Q000737:chemistry / Q000627:therapeutic use*; D010710:Phosphates / Q000737:chemistry*; D010758:Phosphorus; D011073:Polyamines; D011095:Polyethylenes / Q000494:pharmacology*; D011108:Polymers / Q000737:chemistry; D006435:Renal Dialysis / Q000009:adverse effects; D044967:Serum / Q000378:metabolism; D000069603:Sevelamer; D013131:Spine / Q000473:pathology; D013997:Time Factors; D014057:Tomography, X-Ray Computed
D015415:Biomarkers; D004852:Epoxy Compounds; D010281:Parathyroid Hormone; D028044:Phosphate-Binding Proteins; D010710:Phosphates; D011073:Polyamines; D011095:Polyethylenes; D011108:Polymers; D010758:Phosphorus; D000069603:Sevelamer; D000469:Alkaline Phosphatase; D002118:Calcium