Prevention of Secondary Hyperparathyroidism With Vitamin D in Stage II/III Chronic Kidney Disease

This study will evaluate whether earlier intervention with vitamin D in stage II/III chronic kidney disease will prevent or delay secondary hyperparathyroidism. Subjects will receive vitamin D or placebo at study entry and will be followed for a period of one year. The hypothesis is that subjects given vitamin D will have lower PTH and higher 25(OH)D after 1 year compared to placebo. Additionally, there will be less subjects who progress into secondary hyperparathyroidism in the vitamin D treated group compared to the placebo treated group.