Ans. d (Vitamin B12) (Ref. H - 17th/pg. Table 71-1).Vitamins: Major FunctionsVITAMINFUNCTIONVitamin AA component of visual pigment; Maintenance of specialized epithelia; Maintenance of resistance to infectionVitamin DFacilitates intestinal absorption of calcium and phosphorus and mineralization of boneVitamin EMajor antioxidant; scavenges free radicalsVitamin KCofactor in hepatic carboxylation of procoagulants--factors II (prothrombin), VII, IX, and X; and protein C and protein S.Vitamin B1 (thiamine)As pyrophosphate, is coenzyme in decarboxylation reactions. Converted to coenzymes flavin mononucleotide and flavin adenine dinucleotide, cofactors for many enzymes in intermediary metabolismNiacinIncorporated into nicotinamide adenine dinucleotide (NAD) and NAD phosphate, involved in a variety of redox reactionsVitamin B6 (pyridoxine)Derivatives serve as coenzymes in many intermediary reactionsVitamin B12Required for normal folate metabolism and DNA synthesis; Maintenance of myelinization of spinal cord tractsVitamin CServes in many oxidation-reduction (redox) reactions and hydroxylation of collagenFolateEssential for transfer and use of 1-carbon units in DNA synthesisPantothenic acidIncorporated in coenzyme ABiotinCofactor in carboxylation reactionsVitamin B12.introductionStored primarily in the liver. Very large reserve pool (several years). Synthesized only by microorganisms. Found only in animal products.FunctionCofactor for homocysteine methyltransferase (transfers CH3 groups as methylcobalamin) and methyimalonyl-CoA mutase. Abnormal myelin is seen in B12 deficiency, possibly due to | methionine or | methylmalonic acid (from metabolism of accumulated methylmalonyl-CoA).Causes of deficiencyVitamin B12 deficiency is usually caused by malabsorption (sprue, enteritis, Diphyllobothrium latum), lack of intrinsic factor (pernicious anemia, gastric bypass surgery), or absence of terminal ileum (Crohn's disease). Use Schilling test to detect the etiology of the deficiency.Deficiency featuresMacrocytic, megaloblastic anemia; neurologic symptoms (optic neuropathy, subacute combined degeneration, paresthesia); glossitis.PRINCIPAL CLINICAL FINDINGS OF VITAMIN MALNUTRITIONNutrientClinical findingDietary level per day associated with overt deficiency in adultsContributing factors to deficiencyThiamineBeriberi:Neuropathy,Muscle weakness and wasting, Cardiomegaly,Edema,Ophthalmoplegia,Confabulation<0.3 mg/1000 kcalAlcoholism, chronic diuretic use, hyperemesisRiboflavinMagenta tongue,Angular stomatitis,Seborrhea,Cheilosis<0.6 mg-NiacinPellagra:Dermatitis: Pigmented rash with silvery/ varnish-like scales of sun-exposed areas.Bright red beefy tongue.DiarrheaDementiaApathyDisorientationDeath (if untreated)<9.0 niacin equivalentsAlcoholism, vitamin B6 deficiency, riboflavin deficiency, tryptophan deficiencyVitamin B6SeborrheaGlossitisConvulsions (especially in neonates),Neuropathy,Depression,Confusion,Microcytic anemia<0.2 mgAlcoholism, isoniazid (most common cause)FolateMegaloblastic anemia,Atrophic glossitis,Depression, -Homocysteine<100 mg/dAlcoholism, sulfasalazine, pyrimethamine, triamtereneVitamin B12Megaloblastic anemia,SACD:Loss of vibratory and position sense, Abnormal gait,Dementia, impotence,Loss of bladder and bowel control, -homocysteine, -methylmalonic acid.<1.0 mg/dGastric atrophy (pernicious anemia), terminal ileal disease, strict vegetarianism, acid reducing drugs (e.g., H2 blockers)Vitamin CScurvy:petechiae, ecchymosis, coiled hairs, inflamed and bleeding gums, joint effusion, poor wound healing, fatigue, perifollicular hemorrhages, subperiosteal hematoma (Woody leg).<10 mg/dSmoking, alcoholismVitamin AXerophthalmia, night blindness, Bitot's spots,Follicular hyperkeratosis,Impaired embryonic development, Immune dysfunction<300 mg/dFat malabsorption, infection, measles, alcoholism, protein-energy malnutritionVitamin DRickets: skeletal deformation, rachitic rosary, bowed legs; osteomalacia<2.0 mg/dAging, lack of sunlight exposure, fat malabsorption, deeply pigmented skinVitamin EPeripheral neuropathy,Spinocerebellar ataxia,Skeletal muscle atrophy, retinopathyNot described unless underlying contributing factor is presentOccurs only with fat malabsorption, or genetic abnormalities of vitamin E metabolism/transportVitamin KElevated prothrombin time, bleeding<10 mg/dFat malabsorption, liver disease, antibiotic use