Vitamin_D_Metabolism_Complete_Presentation.pptx

Vitamin metabolism

1. Vitamin D Metabolism Presented by : R.ArunaDevi 25MIM049

2. Introduction • Fat-soluble vitamin acting as a prohormone . • Important for calcium & phosphate balance, bone health, immunity . • Obtained from sunlight, diet, and supplements . • Requires activation in liver and kidney .

3. Sources of Vitamin D Endogenous: Skin synthesis (UVB → Vitamin D₃) Exogenous (dietary sources) Vitamin D₂ (plants, fortified foods) . Vitamin D₃ (fish oil, egg yolk, dairy products)

4. Skin • 7-dehydrocholesterol in skin absorbs UVB (290–315 nm) • Converts to Pre-vitamin D₃ • Thermal conversion → Vitamin D₃ (cholecalciferol) • Factors: skin color, age, sunscreen, geography • Vitamin D₃ enters blood bound to DBP → Liver

5. Liver • Enzyme: 25-hydroxylase (CYP2R1) • Vitamin D (D₂ or D₃) → 25-hydroxyvitamin D [25(OH)D, Calcidiol ] • Main circulating storage form • Used for blood tests to assess Vitamin D status

6. Kidney • Enzyme: 1α-hydroxylase (CYP27B1) • 25(OH)D → 1,25-dihydroxyvitamin D [1,25(OH)₂D, Calcitriol] • Active hormone form • Regulated by PTH, calcium, phosphate, and FGF23

7. Regulation • Parathyroid Hormone (PTH): ↑ calcitriol production . • Calcium & phosphate: feedback control . • FGF23: inhibits excess calcitriol production .

8. Functions of Vitamin D • Intestine: ↑ absorption of calcium & phosphate • Bone: promotes mineralization & remodeling • Kidney: reduces calcium excretion • Immune system: modulates defense mechanisms

9. Disorders of Vitamin D Deficiency: - Rickets (children) - Osteomalacia (adults) - Osteoporosis (elderly) Excess: - Hypercalcemia - Kidney stones - Organ damage

10. Clinical Importance • Blood test measures 25(OH)D (not active calcitriol) . • Normal range: 30–50 ng/ mL . • Vitamin D₃ supplements preferred . • Used in osteoporosis, CKD, hypoparathyroidism treatment .

11. Conclusion • Vitamin D acts as a hormone regulating calcium-phosphate balance . • Synthesized in skin, activated in liver & kidney . • Active form (calcitriol) affects intestine, bone, kidney, immune system . • Both deficiency and excess cause health problems .

12. REFERENCE : Holick MF. Vitamin D Deficiency. N Engl J Med. 2007.
DeLuca HF. Overview of general physiologic features and functions of vitamin D. Am J Clin Nutr . 2004. Bikle DD. Vitamin D metabolism, mechanism of action, and clinical applications. Chem Biol. 2014.