Vitamin D receptor (VDR) has an important role in negatively controlling PTH secretion and parathyroid proliferation, thus representing a good target for this parathyroid pathological condition, but no mutations in either VDR gene or vitamin-D-activating enzyme were found in sporadic parathyroid tumors despite the evidence of the reduced expression in some series [62–65]. This evidence concerns the gene VDR and tumor of parathyroid gland.