The Effect of Combined Calcium and Vitamin D3 Supplementation on Serum Intact Parathyroid Hormone in Moderate CKD

Background: Studies addressing the effects of vitamin D-3 supplementation on secondary hyperparathyroidism in patients with moderate chronic kidney disease are scarce. Study Design: Post hoc analysis of the randomized clinical trial Vitamin D, Calcium, Lyon Study II (DECALYOS II) to assess effects according to baseline estimated glomerular filtration rate (eGFR). Setting & Participants: Multicenter, randomized, double-blinded, placebo-controlled study of 639 elderly women randomly assigned to calcium-vitamin D-3 fixed combination; calcium plus vitamin D-3 separate combination, or placebo. Interventions: Placebo or calcium (1,200 mg) and vitamin D-3 (800 IU) in fixed or separate combination. Outcomes & Measurements: Proportion of participants with a mean decrease in intact parathyroid hormone (iPTH) level of 30% or greater. eGFR was calculated using the 4-variable Modification of Diet in Renal Disease (MDRD) Study equation and categorized as 60 or greater, 45 to 59, and less than 45 mL/min/1.73 m(2). Results: 610 participants had an eGFR at baseline: 288 (47.2%), 222 (36.4%), and 100 (16.4%) were in each decreasing eGFR category. Across decreasing eGFR groups, 88%, 86%, and 89% had 25-hydroxyvitamin D (25[OH]D) levels less than 15 ng/mL at baseline. On treatment, similar improvements in the proportion of participants achieving 25(OH)D levels greater than 30 ng/mL at 6 months were seen in all kidney function groups (43%, 49%, and 41%, respectively). Active regimens versus placebo increased mean 25(OH)D levels from baseline in all eGFR groups at all times (P < 0.001 for all). The proportion with a 30% or greater decrease in iPTH level at 6 months was 50% in all eGFR groups on treatment versus 6% to 9% for placebo (P < 0.001 for all). The effects of the intervention on iPTH levels did not differ according to baseline eGFR (interaction P > 0.1 for all times). Limitations: This study included only elderly white women. Conclusion: Vitamin D3 was effective in increasing 25(OH)D and decreasing iPTH levels in patients with moderate chronic kidney disease.