Vitamin D

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Vitamin D

  1. 1. VITAMIN DDr SIVARAJ SDEPT OF PHYSIOLOGYALL INDIA INSTITUTE OF MEDICAL SCIENCESNEW DELHI
  2. 2.  Known as the “Sunshine vitamin” Can be produced in the body, has specific target tissues Dietary requirement is not essential
  3. 3.  Sources sources of vitamin Major source synthesis in the D3, providing only 0.4 to 1 skin ultraviolet B (wavelength mcg/L. 290–315 nm) Vitamin D3 exists naturally in animal products, and the richest sources are fish liver oils Except for fish, food (unless fortified) contains only limited amounts of vitamin D Vitamin D2 (ergocalciferol) is obtained from plant sources and is the chemical form found in some supplements. Human milk and unfortified cows milk tend to be poor
  4. 4.  Absorption, Transport and Storage Vit D+other lipids Micelles Incorporated into chylomicrons Plasma Chylomicron remnants or DBP Liver peripheral tissue
  5. 5. VitaminD3Vit D 25 Hydroxylase
  6. 6.  Functions Maintenance of calcium and phosphorus homeostasis Gene expression In the bone PTH alone or with calcitriol, estrogen, or both, moves calcium and phosphorus from the bone to maintain normal blood levels In the kidney calcitriol increases renal tubular reabsorption of calcium and phosphate.These activities are coordinated with the purpose of maintaining plasma calcium concentrations within a narrow range.
  7. 7.  RDA The AI increases to 10 mcg/day(400IU) for adults age 5l years and older and increases even more to 15 mcg/day( 600IU) for adults 71 years and older The UL for vitamin D for infants is 25 mcg/day (1000 IU) and for children and adults,50mcg/day (2000 IU)
  8. 8.  Deficiency Risk factors• Old age• Lack of sun exposure,• Dark skin• Fat malabsorption• Obesity Rickets Osteomalacia In children in adults
  9. 9.  Rickets Impaired mineralization of growing bones Involves Ca Phosphorus and Vitamin D Clinical features• Bone pain, muscular tenderness, and hypocalcemic tetany• Bowed legs, “knock knees," beaded ribs (the rachitic rosary), pigeon breast, and frontal bossing of the skull Radiology• Enlarged epiphyseal growth plates Treatment Rickets caused strictly by vitamin D deprivation can be treated effectively with oral preparations of the vitamin or natural sources rich in the vitamin
  10. 10.  Osteomalacia Involves generalized reductions in bone density and the presence of pseudofractures, especially of the spine, femur, and humerus Clinical features• Muscular weakness and bone tenderness• Greater risk of fractures, particularly of the wrist and pelvis Prevention Possible with adequate consumption of vitamin D
  11. 11.  Toxicity• Infants and small children are most susceptible to hypervitaminosis D• The UL for vitamin D is 25 mcg (1000 IU)/day for infants and 50 mcg (2000 IU)/day for children and adults.

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