Current activated Vitamin D therapies are approved for treating secondary hyperparathyroidism
in chronic kidney disease (CKD), and a large body of experimental data in animals confirms
the effects of Vitamin D that extend beyond mineral metabolism. Several studies show that the
benefits are greater with the newer vitamin D analog paricalcitol when compared with
calcitriol. A large gap exists in our knowledge between epidemiological studies in human that
demonstrate improved outcomes with vitamin D use and observations in preclinical studies
demonstrating the pleiotropic effects of Vitamin D. To explore the provenance of
epidemiological outcomes in CKD, we conducted a pilot randomized trial to determine whether
the use of paricalcitol, compared to calcitriol, leads to improvement in anemia, a marker
associated with worse outcomes in chronic kidney disease, and whether this effect not only
reflects the hyperparathyroidism correction, but is also dependent on the direct effects of
paricalcitol on erythroid progenitor cells.