Importance of vitamin D receptor activation in clinical practice.

Continuously emerging evidence indicates that defi ciencies in 25-hydroxyvitamin D and consequently vitamin D receptor (VDR) activation play crucial roles in adversely affecting cardiovascular (CV) health in the general population and those at high risk of CV disease, as well as in patients with chronic kidney disease (CKD). In CKD patients, a lack of VDR activation is one of the main pathophysiological factors contributing to secondary hyperparathyroidism (SHPT). However, this lack of VDR activation has numerous additional implications on CV and renal function, with SHPT being only one symptom of a much more extensive disorder. VDRs are widely expressed throughout the body with manifold activities that involve feedback loops within the CV, immune, and renal systems. Modulation of VDR activator levels results in correlative regulatory effects on mineral homeostasis, hypertension, vascular disease, and vascular calcifi cation, as well as a number of other endpoints in cardiac and renal pathology. Among compounds available for the treatment of SHPT, paricalcitol is a selective VDR activator. The term 'selective' refers to paricalcitol being more selective in affecting VDR pathways in the PTH gland compared with bone and intestine. As such, paricalcitol's selectivity allows for a wider therapeutic window with effects beyond PTH control and mineral management, and may explain, in part, the increased survival advantage with paricalcitol treatment.