Vascular Reactivity in Chronic Kidney Disease (CKD) Patients Receiving Paricalcitol Versus Placebo

This research is studying how Vitamin D may affect blood vessels reaction to stress and blood levels of substances that may increase blockages in the blood vessels in chronic kidney disease (CKD) patients. Blood vessel health is worsened in CKD and some studies have shown that Vitamin D improves blood vessel health. The type of Vitamin D being used in this study (paricalcitol) is Food and Drug Administration (FDA) approved to treat high parathyroid hormone levels. The purpose of this study is to find out if paricalcitol has other benefits beyond its ability to lower parathyroid hormone levels such as improving the blood vessels reaction to stress and decreasing blood levels of substances that may increase blockages in the blood vessels.