VDR and Hypercalcemia: These vitamin D analogues (VDAs) include paracalcitol, doxercalciferol, and alfacalcidol, and they have different molecular structures than active vitamin D (side chains or other modifications), which allows them to bind selectively to VDR in the parathyroid glands and therefore reduce the risk of hypercalcemia and hyperphosphatemia while suppressing PTH levels in a dose-dependent manner.