NEW YORK (Reuters Health) – Dietary supplementation with vitamin D3 (cholecalciferol) reduces manifestations of secondary hyperparathyroidism in patients with moderate chronic kidney disease, researchers report in the March issue of the American Journal of Kidney Disease.

“This study,” senior investigator Dr. Michel Chonchol told Reuters Health, “is one of very few studies that evaluates the effects of cholecalciferol administration on intact parathyroid hormone levels in chronic kidney disease patients, with a follow-up of 24 months and comparison with a placebo group.”

Dr. Chonchol of the University of Colorado Denver Health Sciences Center and colleagues studied 639 elderly women who were randomized to receive 1200 mg of calcium and 800 IU of vitamin D3 either in a single combination tablet or in separate tablets, or placebo.

Compared to placebo, the active treatment significantly increased mean 25-hydroxyvitamin D levels from baseline in all participants across all levels of estimated glomerular filtration rate.

The results also showed that, at 6 months, “up to 50% of patients have more than a 30% decrease in parathyroid hormone levels from baseline, which has not been previously reported,” said Dr. Chonchol. By comparison, there was a 6% to 8% drop in placebo patients.

The effectiveness of cholecalciferol did not vary according to the level of kidney function, the researchers point out, and the benefit persisted for up to 24 months after the start of replacement therapy.

“This study should serve as groundwork in doing other studies to evaluate the effects of cholecalciferol in more advanced stages of chronic kidney disease,” Dr. Chonchol concluded.

Am J Kidney Dis 2009;53:408-416.