Vitamin D, Insulin Resistance and Inflammation in ESRD

Inclusion Criteria: * CKD and receiving hemodialysis for ≥ 3months * Kt/V ≥ 1.2 * ≥ 18 years of age * Medically stable * AVF or PTFE dialysis access * No acute inflammatory disease within 4 weeks prior to the study * On stable dose of Paricalcitol for 4 weeks prior to the study * iPTH value between 150 - 1500 within the past 3 months * Ca \< 10.5 * PO4 \< 10 Exclusion Criteria: * Pregnancy * Intolerance to the study medication * Severe, unstable, active, or chronic inflammatory disease (active infection, active connective tissue disorder, active cancer, HIV, liver disease) * Type 1 Diabetes mellitus * Uncontrolled Type 2 Diabetes mellitus (HbA1c \> 10) * Hospitalization within 1 month prior to the study * Malfunctioning arterial-venous vascular access (recirculation and/or blood flow \< 250 ml/min) * Presence of hemodialysis catheter * Patients receiving steroids and/or other immunosuppressive agents (\> 10 mg prednisone qd) * BMI \< 25 and \> 45