VDR and secondary hyperparathyroidism: Therefore, its deficiency often results in bone mineral disorders and in the development of secondary hyperparathyroidism (SHPT) due to the decreased parathyroid levels of vitamin D receptor (VDR) and calcium sensing receptors (CaSRs) with consequent reduction of the inhibitory stimuli on PTH secretion and parathyroid sensitivity to ionized calcium [6,7,8].