[Guidelines for vitamin D prescription in dialysis patients]

The vitamin D hormonal system is involved in the regulation of more than 800 genes. Vitamin D deficiency, which is evaluated on the basis of the serum level of 25-hydroxycholecalciferol (25[OH]D), is frequently observed in the general population, particularly in patients with chronic kidney disease (CKD). Vitamin D deficiency is associated with an increased risk of falls and fracture and also with diabetes, malignancies, autoimmune diseases, depression and mortality. Furthermore, CKD is accompanied by a decrease in the renal production of 1,25 dihydroxycholecalciferol (1,25[OH](2)D). Such deficiencies have also been implicated in the pathophysiology of secondary hyperparathyroidism. Currently, vitamin D supplementation is not recommended in stage 5 CKD. However, since there is also significant extra-renal production of 1,25(OH)(2)D this would appear to be in favour of vitamin D treatment. We describe the disturbances of vitamin D metabolism occurring in CKD and discuss the advantages and the potential toxicity risk of vitamin D supplementation as well as the optimal serum 25[OH]D level. We then present the pharmacological properties of the various medicinal forms of vitamin D derivates and suggest therapeutic guidelines for supplementation with 25(OH)D(3) or cholecalciferol. We also examine existing guidelines for the administration of active 1-alpha-hydroxylated vitamin D. Despite the absence of strong scientific support by randomized controlled intervention studies, vitamin D supplementation should be considered in patients with CKD stages 4-5D having vitamin D insufficiency or deficiency, for the prevention of secondary hyperparathyroidism and for other potential benefits owing to its pleiotropic effects.