Calcium absorption response to cholecalciferol supplementation in hemodialysis

Background and objectives Recent understanding of extrarenal production of calcitriol has led to the use of more vitaminD supplementation in CKD populations. This paper reports the effect of cholecalciferol supplementation on calcium absorption. Design, setting, participants, & measurements Paired calcium absorption tests were done before and after 12-13 weeks of 20,000 IUweekly cholecalciferol supplementation in 30 participants with stage 5 CKD on hemodialysis. The study was conducted from April to December of 2011. Calcium absorption was tested with a standardized meal containing 300 mg calcium carbonate intrinsically labeled with ⁴⁵Ca; 25-hydroxyvitamin D and 1,25- dihydroxyvitamin D were measured. Results 25-Hydroxyvitamin D rose from 14.2 ng/ml (11.5-18.5) at baseline to 49.3 ng/ml (42.3-58.1) at the end of the study (P<0.001). 1,25-Dihydroxyvitamin D rose from 15.1 (10.5-18.8) pg/ml at baseline to 20.5 (17.0-24.7) pg/ml at the end of the study (P<0.001). The median baseline calcium absorption was 12% 7%-17%) and 12% (7%-16%) at the end of study. Conclusions Patients with stage 5 CKD on hemodialysis had very low calcium absorption values at baseline, and cholecalciferol supplementation that raised 25(OH)D levels to 50 ng/ml had no effect on calcium absorption.