Native and active vitamin D [Natives und aktives Vitamin D]

Vitamin D deficiency or insufficiency (defined as serum 25-hydroxyvitamin D levels <30 ng/ml) is frequent in chronic kidney disease (CKD) patients. Supplementation with native vitamin D to achieve high-normal levels (30-50 ng/ml) appears to be clinically safe and results in moderate parathyroid hormone (PTH) suppression, at least in earlier CKD stages but apparently not in CKD 5D. The therapeutic effects of calcitriol and active vitamin D analogs on secondary hyperparathyroidism (sHPT) and hyperparathyroid bone disease are well documented but clinically relevant differences between the various active vitamin D therapeutics have not yet been demonstrated. Noncalciotropic (pleiotropic) effects of the vitamin D system continue to be widely discussed. Newer data suggest that vitamin D deficiency may be related to accelerated renal progression, and one possible pathogenetic mechanism may be reduction of proteinuria by active vitamin D (paricalcitol). In CKD, vitamin D deficiency is associated with increased (cardiovascular) morbidity and mortality and active vitamin D therapy is associated with lower mortality in CKD; however, causal relationships in CKD patients have not yet been demonstrated. © 2013 Springer-Verlag Berlin Heidelberg.