Vitamin D Lecture 2 BIOCHEMISTRY
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Vitamin D Lecture 2 BIOCHEMISTRY

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Vitamin D Lecture 2 BIOCHEMISTRY Vitamin D Lecture 2 BIOCHEMISTRY Presentation Transcript

  • Dr. Vijay Marakala, MBBS, MD. Assistant professor BIOCHEMISTRY SIMS & RC Sunshine vitamin
  • Chemistry Sources RDA Metabolism Functions Deficiency Toxicity
  • PROVITAMIN 7- Dehydrocholesterol Ergosterol VITAMIN Vitamin D3 [Cholecalciferol] Vitamin D2 [Ergocalciferol] Vitamin D is a sterol
  • 200 – 400 IU /day [5 – 10µg/day] 1microgram of vitamin D = 40 International Units
  • Forms D3 D2 Site Upper small intestine Mechanism Along with lipids Requires bile salts ABSORPTION
  • TRANSPORT Binding to vitamin D binding globulin
  • Synthesis of active form of vitamin D 1, 25-dihdroxy cholecalciferol or calcitriolACTIVE FORM
  • 1- α- hydroxylase
  • Calcitriol is the biologically active form of vitamin D Regulation of plasma calcium and phosphorus
  • Action of calcitriol on the intestine Action of calcitriol on the bone Action of calcitriol on the kidney
  • Action of calcitriol on the intestine • Increases the intestinal absorption of calcium and phosphate • By increased synthesis of calcium binding protein
  • Action of calcitriol on the bone • Mineralization of bone at low doses • Mobilization of calcium from bone at high doses
  • Action of calcitriol on the kidney • Increased reabsorption of calcium and phosphorus • Decreased excretion of calcium and phosphorus
  • Causes Inadequate supply Impaired absorption Impaired production of 25hydroxy vitamin D3 Impaired production of 1, 25 dihydroxy vitamin D3 Resistant to the effects of 1, 25 dihydroxy vitamin D3
  • CLINICAL FEATURES Children Adults Children Rickets Adults Osteomalacia
  • Features Delayed milestones Delayed closure of anterior fontanelle Delayed dentition Deformities of bones Decreased serum calcium
  • Bone deformities Craniotabes Frontal bossing Rachitic rosary Pegion chest Knocked knee Bowed legs
  • Frontal bossing
  • Fig. 7-5a, p. 222 Bowed legs – Characteristic of rickets
  • Fig. 7-5b, p. 222 Beaded ribs – Characteristic of rickets
  • Rachitic rosary
  • Causes Inadequate exposure to sunlight Inadequate dietary intake Features Demineralization occurs mainly in spine, pelvis and lower extremities Increased softness & susceptibility to fracture Bowing of long bones
  • Causes Over ingestion Features Hyper calcemia Metastatic calcification