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Vitamin d
This document discusses vitamin D, calcium, parathyroid hormone, and calcitonin. It covers their roles in calcium regulation and bone health. Vitamin D is a fat-soluble vitamin that is synthesized in the skin from cholesterol or ingested from plants and animals. It is metabolized in the liver and kidneys to its active form calcitriol, which increases calcium absorption from the intestine and bone resorption. Parathyroid hormone increases serum calcium levels by promoting bone resorption and renal calcium reabsorption. Calcitonin has the opposite effect of parathyroid hormone by inhibiting bone resorption and promoting calcium deposition in bone. Together these elements work to maintain adequate calcium levels in the blood
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Vitamin d
- 1.
- 2. INTRODUCTION Fat soluble vitamin Sterol Functionlike hormone • Forms Ergocalciferol – vitamin d2 Cholecalciferol – vitamin d3
- 3. • Distribution Ergocalciferol –plants Cholecalciferol – animals Referred as pro vitamin They differ from each other only in presence of additional double bond and methyl group
- 5. Cholesterol biosynthesis 7dehydrocholesterol Sun Cholecalciferol
- 6. ABSORPTION • Absorbed insmall intestine Vit d2 and d3 mixed with micelles by combining with bile salts Mixed micelles are presented to mucosal cells Absorption by passive transport
- 7.
- 8. METABOLISM • Cholecalciferol hydroxylatedat 25th position to 25 hydroxy cholecalciferol in liver • 25 hydroxy cholecalciferol at position 1 to form 1,25 dihydroxy cholecalciferol and at 24 position to form 24,25 dihydroxy cholecalciferol • It has 3 carbons 1,3 and 25 hence called calcitriol
- 10. REGULATION • 1,25 dihydroxycholecalciferol is regulated by 1 alpha hydroxylase • Its activity is increased in hypocalcemia Which inturn stimulates pth secretion leading to increase 1 alpha hydroxylase
- 12. RDA • Children -10 mg/day or 400 iu • Adults – 5 mg /day or 200 - 10 mg/day or 400 • >60 yrs – 600 iu
- 14. FUNCTION MAINTAIN ADEQUATE LEVELOF CALCIUM IN PLASMA • INCREASE UPTAKE OF CALCIUM BY ABSORPTION FROM INTESTINE • VIT D ALONG WITH PARATHYROID HARMONE HELPS IN BONE FORMATION WHICH CAUSES ELEVATION OF CALCIUM • MINIMIZE THE EXCRETION PF CALCIUM AND PHOSPHATES AND ENHANCING REABSORPTION
- 15. CLINICAL IMPORTANCE • Nutritionalrickets Demineralization of bone Decreased serum calcium (9 – 11 mg / dl) Decreased plasma phosphorous (3 to 4.5 mg /dl)
- 17. • Renal rickets Chronicrenal failure Inability to synthesis 1 alpha hydroxylase • High consumption Calcinosis Loss of appetite Nausea Lathergy Loss of weight
- 18.
- 19. INTRODUCTION • Most abundant 1– 1.5 kg 99% Bone and teeth 1% Skeletal tissue
- 21. BIOCHEMICAL FUNCTION • Development •Muscle contraction • Blood coagulation • Nerve transmission • Membrane integrity and permeability • Activation of enzyme • Release of hormone • Secretory process • Contact inhibition • Action on heart
- 22. DIETARY REQUIREMENT • ADULT– 800 mg 1.5 gm • CHILDREN - .8 TO 1.2 g • INFANTS – 300 TO 500 mg
- 23. • Calcitriol • PTH •Calcitonin
- 24. SOURCE • BEST MILK ANDmilk products • GOOD BEANS VEGETABLES FISH EGG YOLK CABBAGE
- 27.
- 28. PARATHYROID HARMONE • Secretedby 2 pairs of parathyroid glands Single chain polypeptide 84 amino acids PREPRO PTH 115 PRO PTH 90 ACTIVE PTH 84
- 29. MECHANISM • PRIME FUNCTION ELEVATESERUM CALCIUM • 3 INDEPENDENT TISSUE Bone Kidneys Intestine
- 30. • Bone Demineralization ofbone by osteoclasts Increased activity of Enzymes pyrophosphates and collagenase • Kidneys Increases ca resorption Promoting production of calcitriol • Intestines Synthesis of calcitriol
- 31. • Excess activityof the parathyroid gland causes rapid absorption of calcium salts from the bones, with resultant hypercalcemia in the extracellular fluid • conversely, hypofunction of the parathyroid glands causes hypocalcemia, often with resultant tetany.
- 32.
- 34.
- 35. CALCITONIN • Peptide 32 AA Antagonistof PTH mechanism Promotes calcification ( osteoblast ) Decreases bone resorption and increases calcium excretion
- 37. CLINICAL IMPORTANCE • Hypercalcemia •Hypocalcemia • Rickets • Renal rickets • Osteoporosis • Osteopetrosis • Paget’s disease , in which osteoclastic activity is greatly accelerated, calcitonin has a much more potent effect of reducing the calcium absorption.
Editor's Notes
- #9 1,25 DIHYDROXY CHOLECALCIFEROL ACTIVE FORM 24.25 DIHYDROXY CHOLECALCIFEROL
- #11 LEADS TO RENAL RICKETS
- #16 ENLARGEMENT AND SOFTENING OF BONE DELAY IN TEETH FORMATION WT BEARING BONES ARE BENT DEC CALCIUM POT BELLY
- #33 PTH ↑calcium and phosphate absorption from the bone PTH ↓excretion of calcium by the kidneys. PTH ↑renal phosphate excretion