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 D(3) was effective in increasing 25(OH)D and decreasing iPTH levels in patients with moderate chronic kidney disease.