2. Outline
•Introduction
•Vitamins A, D, E & K
•Chemical forms
•Sources
•Normal values
•General functions
•Deficiency/Excesses & Rx
•Biochemical assay
•Conclusion
•References
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3. Introduction
•Vitamins are organic compounds required in trace
amounts (usually micrograms to milligrams per day)
in the diets for health, growth and reproduction.
•They are chemical compounds necessary for proper
functioning of the human body.They regulate
chemical reactions of intermediary metabolism, as
well as important substrates in biosynthesis.
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4. •They can be classified as either water-soluble or fat-
soluble.
•Water soluble vitamins: not stored; urinary excretion
must be provided regularly; deficiency can develop
easily.
•Fat soluble vitamin: stored; accumulates in the liver
and adipose tissues.
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7. 20-carbon structure with cyclohexeynl ring and
isoprenoid side chain and terminal groups:
•Hydroxyl group: Retinol
•Aldehyde group: Retinal
•Ester group: Retinyl ester
•Carboxylic group: Retinoic acid
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VITAMIN A
8. •Retinol, the principal form of vitamin A, can be oxidized
reversibly to retinal – or to retinoic acid.The storage
form of vitamin A are the retinyl esters.
•The term retinoids refers to retinols, its metabolites and
synthetic analogs. Also included in theVit. A family are
some dietary pro-vitamin A carotenoids (C40-
compounds) mostly beta-carotenes.
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9. •Beta-carotene is a vitamin A precursor
•β-carotene is converted to vitamin A in the intestinal
mucosa and absorbed, packaged into chylomicrons.
•90% is stored in liver, mainly as retinyl ester; small
amounts in adipocyte and blood.
•Transport: Retinol binding protein(RBP).
•Excretion: Small amount in urine
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12. General role of Vit. A
•Most significant function: vital to good vision
•Necessary for healthy skin, hair growth
•Functions in reproduction and growth of
embryo
•Keeps mucous membrane regeneration
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13. • Participation of the A
vitamers in the visual
cycle is the mot
important
physiologic function
of vit. A.
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14. Deficiency of Vit. A
•Nyctalopia
•Cell keratinization:
•Keratomalacia
•Xerophthalmia
•Bronchopulmonary dysplasia in premature infants
•In adults, retinol intakes of 500 – 600 mcg are required
to maintain adequate blood conc. and to prevent
deficiency symptoms
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16. Conjunctival Xerosis
Corneal Xerosis
Keratomalacia followed by Blindness
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Recommended xerophthalmia treatmentschedule
6 -12 months > 1 yr
Immediately 100,000 IU 200,000 IU
Nextday 100,000 IU 200,000 lU
2–4 weekslater 100,000 IU 200,000 IU
17. Vitamin A Prophylaxis Programme
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Individual Oral dose Timings
0-6 m0nths infants 25,000 IU retinyl
palmitate
1 – 3 times over the1st
6months of life
6-11 months children 100,000 IU retinyl
palmitate
Once every 4 to6
months
> 12 months old 200,000 IU retinyl
palmitate
Once every 4 to6
months
Women of child
bearing age
2oo,ooo IU retinyl
palmitate
With in onemonth of
giving birth
Pregnant and
lactating women
5,000 to 10,000 IU
retinyl palmitate
Daily
18. Excess of Vit. A
•Hypervitaminosis A:
•Storage forms exceeds 3000 mc/g of tissue
•Ingestion over 30,000 mcg/d for >= 1month
•Plasma conc exceeds 140 mcg/dL (4.9 umol/L)
•Self medication, over-prescription
•Symptoms of toxicity:
•Dry itchy skin, hepatomegaly, benign intracranial
hypertension, reduction of bone mineral density.
•Mgt: discontinueVit. A containing subst. and treat
arisen complications.
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19. Biochemical assay
Plasma conc. not an ideal indicator, as it does not
decline until liver store becomes critically depleted.
•Circulating retinol conc. do not always correlate with
body stores ofVit. A, indirect testing procedures are
employed for assessment of body vitamin A:
•Two-blood samples; one before, and 5-hrs after a
physiologic dose of vitamin A.
•Dose response analysis made.
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23. VITAMIN D
•There are 2 major precursor forms:
•Ergosterol
•7-dehydrocholesterol
•Vitamin D2 = ergocalciferol: synthetic form produced
by irradiation of the plant steroid ergosterol.
•Vitamin D3 = cholecalciferol: Produced
photochemically by the action of sunlight or ultraviolet
light from the precursor sterol 7- dehydrocholesterol.
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24. Sources
•Also known as bone
vitamin
•Synthesized in body
•Plants (ergosterol)
•Fortified milk products
•Egg yolk, Liver
•Butter, Oily fish
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25. Normal values
Recommended Dietary Allowances
Adult male-- 15mcg (600IU)
Adult female—15mcg
Pregnancy and lactation–15mcg
Normal plasma level of vitamin D: 10 - 55 ng/mL
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26. Formation of vitamin D
•Skin (UV light)
•7-dehydro cholesterol → vitamin D3
• Liver: OH-group added
•25-hydroxy vitamin D3
•Stores vitamin (~3 months storage in liver)
•Kidney: OH-group added by 1-hydroxylase
•1,25-dihydroxy vitamin D3 or 1,25-dihydroxy
cholecalciferol, (1,25-DHCC)…active form of vitamin D.
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28. Functions of Vitamin D
•Calcium and Phosphorus Homeostasis
•Calcium and Phosphorus absorption (smallintestine)
•Calcium resorption (bone andkidney)
•Maintain blood calciumlevels
•Bone formation
• Stimulate calcium uptake for deposition as calcium
phosphate (Osteoblasts: bone-forming cells)
•Hormone: Regulation of geneexpression, Cellgrowth
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29. Deficiency ofVit. D
• Children
• Rickets (meaning: twist)
• Failure of bones to growproperly
• Results in “bowed” legs or knock-knees, outward bowed
chest and knobs on ribs
• Adults
• Osteomalacia (Greek: osteon-bone,malakia-softness):
• Adult form ofrickets
• Osteoporosis (porous bones):
• Loss of vitamin D activity with advancingage
• Associated with fractures very serious forgeriatrics
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30. 30
Rickets
The National Osteoporosis Foundation recommends vitamin D 400 IU to 800 IU
daily for adults under age 50, and up to 1000 IU daily for older adults for preventing
osteoporosis and fractures.
31. Toxicity
• Hypervitaminosis D
• Among the vitamins, vitamin D is the most toxic in
overdoses (10-100 times RDA)
• Calcification of softtissue
• Lungs, heart, bloodvessels
• Hardening of arteries, stone formation inkidneys
Does not occur from sunlight or dietary sources
Does occur with supplementation
• Upper limit: 50 micrograms aday.
• Nausea/vomiting, poor appetite
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32. Management of hypervitaminosis D
•Stop taking high-dose vitamin A supplements.
Most people make a full recovery within a few
weeks.
•Any complications that occurred from the excess
vitamin A, such as kidney or liver damage, will be
treated independently
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34. •Serum is typically used for measuring vitamin D and
metabolites, although plasma generally is acceptable
for assays using extraction and chromatography.
•Once separated from the clot, serum is relatively
stable at both room temperature and 4°C; specimens
should be frozen if the analysis is delayed.
•Vitamin D metabolites in serum or plasma do not
appear to be sensitive to light and do not require
special handling in the laboratory.
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36. VITAMIN E
• A naturally occurringantioxidant.
• Anti-sterilityvitamin.Tocopherol (Greek: tokos-
child birth; pheros-bear; ol-alcohol).
• The term vitamin E refers to a family of 8
related compounds, the tocopherols;
• The four major forms are designated ,
of which -tocopherol is the most active.
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39. • Absorption andTransportation
• Micelles into chylomicrons
• Transported via lipoproteins
• Stored in adipose tissue
• Excretion: Bile, urine and skin
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40. General functions of Vit. E
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•Antioxidant
•Free radical scavenger
•Protects cell membrane integrity.
•Protects RBCs from hemolysis.
• Essential for normal reproduction in humans.
• Preserves & maintains germinal epithelium of
gonads.
41. Deficiency states
•Vitamin E deficiency causes
•Lipid peroxidation, resulting in red blood cell fragility
and hemolytic anemia (mostly in the newborn and
premature).
•For vitamin E deficiency: dose in adults is alpha
tocopherol 60-75 IU per day.
•Evion drops -50mg/ml for children.
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42. Excess / Vit. E Toxicity
Hypervitaminosis E
Toxicity rare: wide range of safe intake
compared to other fat soluble vitamins.
Severe symptoms rarely seen inhumans.
Tendency of hemorrhage.
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44. Biochemical assay ofVit. E
•Early indirect procedures: protection of
erythrocyte hemolysis on addition of peroxide;
inhibition of lipid peroxidation method
•Currently, direct measurement of serum vitamin E
level: Photometry, Fluorometry, or High
performance liquid chromatography (method of
choice)
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46. VITAMIN K
• A fat soluble vitamin with a very
important hematological function.
• Required for the production of blood
clotting factors, essential for coagulation.
Named as antihemorrhagic vitamin.
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47. Sources
• Plant sources
• Green leafy vegetables
• Some oils, fortified
• Broccoli, Apples, Pears
• Animal sources
• Liver
• Milk
• Also made by bacteria in the gut
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48. …Vit. K
•RDA: 80 µg for men, 65 µg for women
•3 compounds with biological activity of vitamin K
• K1, phylloquinone
• Chloroplasts in plants
• K2, menaquinone
• Bacterialsynthesis
• K3, menadione:
•Synthetic, can be metabolized to phylloquinone.
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49. General role
•Essential for clotting of blood.
•Clotting factors are synthesized in the liver as inactive
precursors - vitamin K converts them to their active forms
• Absorbed in small intestine, via chylomicrons in
lymphatic system.
•Transported via lipoproteins and stored in theliver
•Excretion, Primarily via bile, small amount in urine.
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50. Deficiency states
•Increases clotting time, bleeding & hemorrhage
•Hem0rrhagic disease of the newborn.
•Conversion of prothrombin to thrombin, an
active enzyme
•Formation of fibrinogen to fibrin, leading to clot
formation
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52. Biochemical assay…Vit. K
•Direct measurement of plasma phylloquinone is the
best indicator of vitamin K status, as it has been shown
to correlate with intake & storage.
•Reference interval for plasma vit. K is 0.13 – 1.19 ng/mL
•High performance liquid chromatography
•HPLC-MS as reference method
•Radioimmunoassay
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53. …summary 53
CPB: Competitive protein binding, HPLC: high-performance liquid chromatography, PIVKA: protein
induced by vitamin K absence or antagonism, RIA: radioimmunoassay
54. REFERENCES
•Tietz ClinicalChemistry and Molecular Diagnostics, 5th Ed
•Bishops Clinical Chemistry – Principles,Techniques,
Correlations, 7th Ed.
•Martin A. Crook; ClinicalChemistry and Metabolic Medicine,
5th Edition
•Harrison’s Principles of Internal Medicine, McGraw-Hill, New
York, NY, 20th Ed.
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