The delicate balance between vitamin D, calcium and bone homeostasis: Lessons learned from intestinal- and osteocyte-specific VDR null mice

▸ 1,25(OH)2D promotes intestinal calcium transport during normal/low calcium intake. ▸ High 1,25(OH)2D levels minimize skeletal calcium content to maintain normocalcemia. ▸ High 1,25(OH)2D levels increase bone resorption leading to osteopenia. ▸ Increased VDR signaling in osteoblasts/osteocytes suppresses bone mineralization.