Chronic kidney disease (CKD) is an established risk factor for cardiovascular morbidity and mortality, as shown by common manifestations of left ventricular hypertrophy (LVH) and arterial calcifications in CKD patients. Fibroblast growth factor-23(FGF-23) is a recently identified phosphaturic hormone that has been reported to be associated with the development of secondary hyperparathyroidism, cardiovascular morbidity, mortality, CKD progression.

While vitamin D is the mainstay therapy in CKD mineral bone disease (CKD-MBD), increased FGF-23 levels have been reported with vitamin D administration. The purpose of this study was to investigate the effect of calcium carbonate when used in conjunction with calcitriol on FGF-23.

Inclusion Criteria:

• Adults of 18~70 years of age
• CKD stage 3 patients (GFR: 30-60ml/min/1.73m2)
• Patients who've given consent to the trial

Exclusion Criteria:

• Known allergy to Vitamin D or calcium carbonate
• Administration of vitamin D analogue or phosphate binders 3 months prior to study entry
• History of hypercalcemia (corrected serum calcium > 10.5 mg/dL) or hypophosphatemia (serum phosphate < 2.5 mg/dL) 3 months prior to study entry
• Patients with bone pathologies or diseases requiring vitamin D therapy that is unrelated to CKD-MBD
• Administration of concurrent medication , diseases, or history of surgeries that may affect bone-mineral metabolism or alter bone status
• Patients diagnosed with rapidly progressive glomerulonephritis(RPGN) or those in need of renal replacement therapy
• Patients with obstructive bowel diseases, or severe gastrointestinal diseases
• Patients with less than 2 years of life expectancy(ex. Malignancy diseases)