BACKGROUND: Chronic kidney disease (CKD) is associated with elevations in serum phosphate, calcium-phosphorus product and bone-specific alkaline phosphatase (BAP), with attendant risks of cardiovascular and bone disorders.
Active vitamin D can suppress parathyroid hormone (PTH), but may raise serum calcium and phosphate concentrations. Paricalcitol, a selective vitamin D activator, suppressed PTH in CKD patients (stages 3 and 4) with secondary hyperparathyroidism (SHPT) with minimal changes in calcium and phosphate metabolism.
METHODS: The VITAL study enrolled patients with CKD stages 2-4. We examined the effect and relationship of paricalcitol to calcium and phosphate metabolism and bone markers in a post hoc analysis of VITAL. The study comprised patients with diabetic nephropathy enrolled in a double-blind, placebo-controlled, randomized trial of paricalcitol (1 or 2 μg/day). Urinary and serum calcium and phosphate, serum BAP, and intact PTH (iPTH) concentrations were measured throughout the study.
RESULTS: Baseline demographics and calcium, phosphate, PTH (49% with iPTH < 70 pg/mL), and BAP concentrations were similar between groups. A transient, modest yet significant increase in phosphate was observed for paricalcitol 2 μg/day (+0.29 mg/dL; P < 0.001). Dose-dependent increases in serum and urinary calcium were observed; however, there were few cases of hypercalcemia: one in the 1-μg/day group (1.1%) and three in the 2-μg/day group (3.2%). Significant reductions in BAP were observed that persisted for 60 days after paricalcitol discontinuation (P < 0.001 for combined paricalcitol groups versus placebo). Paricalcitol dose-dependent reductions in iPTH were observed. Paricalcitol in CKD patients (±SHPT) was associated with modest increases in calcium and phosphate.
CONCLUSION: Paricalcitol reduces BAP levels, which may be beneficial for reducing vascular calcification.
Written by:
Coyne DW, Andress DL, Amdahl MJ, Ritz E, de Zeeuw D. Are you the author?
Division of Renal Diseases, Washington University School of Medicine, St Louis, MO, USA.
Reference: Nephrol Dial Transplant. 2013 Jun 19. Epub ahead of print.
doi: 10.1093/ndt/gft227
PubMed Abstract
PMID: 23787544
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