Why Vitamin D Important and what are its Physiologic functions?
Vitamin D maintains calcium homeostasis, maximizes intestinal absorption of calcium (In vitamin D-sufficient people: 30% of calcium is absorbed from the diet while in vitamin D-deficient people: 10-15% of calcium is absorbed from the diet), maintains phosphate homeostasis. Vitamin D Deficiency results in increased production and excretion of PTH (parathyroid hormone) or secondary hyperparathyroidism. Vitamin D plays its role in musculoskeletal as well as extraskeletal organs. Musculoskeletal Effects include maintenance of normal musculoskeletal function (Skeletal muscle has receptors (VDR) for 1, 25(OH) 2D3, Severe vitamin D deficiency is associated with muscle weakness, limb pain & impaired physical function). Secondary hyperparathyroidism, associated with Vitamin D Deficiency, causes an increase in bone resorption (calcium released from bone) and may precipitate or exacerbate osteoporosis. In more severe vitamin D deficiency, secondary hyperparathyroidism & low calcium X phosphate pr
