Vitamin D supplementation in renal disease: is calcitriol all that is needed?

Vitamin D not only plays important roles in mineral metabolism, but also affects the risk of mortality and cardiovascular events. Since the kidney is the main organ that produces 1,25-dihydroxyvitamin D, active vitamin D sterols are widely used in patients with chronic kidney disease (CKD), especially those with secondary hyperparathyroidism. CKD patients also have higher risk of vitamin D deficiency, due to urinary loss associated with proteinuria and possible down-regulation of megalin in the proximal tubular cells. Accordingly, it is reasonable to supplement nutritional vitamin D in CKD patients with vitamin D deficiency. Although still unclear, it has been suggested that local 1α-hydroxylase activity plays more significant roles in CKD patients compared to those with normal kidney function. Future studies should examine whether correction of vitamin D deficiency, administration of active vitamin D, or both, provides survival benefits in patients with CKD.