Vitamins Flashcards
For each vitamin, name the function and symptoms of deficiency and excess.
Vitamin A (Retinol)
Function: Antioxidant; constituent of visual pigments; essential for normal differentiation of epithelial cells into specialized tissue (pancreatic cells, mucus-secreting cells); prevents squamous metaplasia. Used to treat measles and AML, topically for acne. Found in liver and leafy veggies.
Deficiency: Night blindness; dry, scaly skin (xerosis cutis); alopecia; corneal degeneration (keratomalacia); immune suppression.
Excess: Arthralgias, skin changes (scaliness), alopecia, cerebral edema, pseudotumor cerebri, osteoporosis, hepatic abnormalities. Teratogenic (cleft palate, cardiac abnormalities).
Vitamin B1 (thiamine)
Function: Thiamine pyrophosphate (TPP) is a cofactor for pyruvate dehydrogenase, a-ketoglutarate dehydrogenase, transketolase, and branched-chain ketoacid dehydrogenase.
Deficiency: Impaired glucose breakdown leads to ATP depletion, worsened by glucose infusion, with highly aerobic tissues (heart, brain) affected first. Seen in malnutrition and alcoholism. Diagnosed by increased RBC transketolase activity following B1 administration.
- Wernicke-Korsakoff syndrome: confusion, ophthalmoplegia, ataxia, confabulation, personality change, permanent memory loss, due to damage of mammillary bodies and medal dorsal nucleus of thalamus.
- Dry beriberi: polyneuritis, symmetric muscle wasting.
- Wet beriberi: high output cardiac failure (dilated myopathy), edema.
Hints: ATP = A-ketoglutarate dehydrogenase, Transketolase, Pyruvate dehydrogenase. Ber1Ber1. W-K: “eyes, lies, capsize”
Vitamin B2 (riboflavin)
Function: Component of flavins FAD and FMN, used as cofactors in redox reactions.
Deficiency: Cheilosis (inflammation of lips, scaling and fissures at corners of mouth), corneal vascularization.
Hints: the 2 C’s of B2.
Vitamin B3 (niacin)
Function: Constituent of NAD+ and NADP+. Derived from tryptophan. Synthesis requires B2 and B6. Used to treat dyslipidemia - lowers levels of VLDL and raises HDL.
Deficiency: Glossitis. Severe deficiency leads to pellagra, caused by Hartnup disease (decreased tryptophan absorption), malignant carcinoid syndrome (increased tryptophan metabolism), and isoniazid (decreased B6). Symptoms are the 3 D’s: diarrhea, dementia (with hallucinations), dermatitis.
Excess: Facial flushing (prostaglandin), hyperglycemia, hyperuricemia
Vitamin B5 (pantothenate)
Function: essential component of CoA and fatty acid synthase.
Defiency: dermatitis, enteritis, alopecia, adrenal insufficiency.
Hint: B5 is “pento”thenate
Vitamin B6 (pyroxidine)
Function: Converted to pyridoxal phosphate, a cofactor used in transamination decarboxylation reactions, glycogen phosphorylase. Synthesis of cystathionine, heme, niacin, histamine, and neurotransmitters.
Deficiency: Convulsions, hyperirritability, peripheral neuropathy, sideroblastic anemias due to impaired hemoglobin synthesis and iron excess. Inducible by isoniazid and oral contraceptives.
Vitamin B7 (biotin)
Function: Cofactor for carboxylation enzymes pyruvate carboxylase, acetyl-CoA carboxylase, and propionyl-CoA carboxylase
Deficiency: Dermatitis, alopecia, enteritis. Caused by antibiotics or excessive ingestion of raw egg whites. Rare.
Vitamin B9 (folic acid)
Function: Converted to THF, important in synthesis of DNA/RNA bases. Found in leafy greens, absorbed in jejunum.
Deficiency: Macrocytic, megaloblastic anemia; hypersegmented PMNs; glossitis; no neuro symptoms. Labs show high homocysteine and normal MMA. Most common vitamin deficiency in the US. Common in alcoholics and pregnancy. Can also be caused by durgs. Deficiency in pregnancy leads to neural tube defects.
Vitamin B12 (cobalamin)
Function: cofactor for homocysteine methyltransferase and methylmalonyl-CoA mutase. Go look at the pathway. Do it now. Seriously. Found in animal products, synthesized only by microorganisms, several years worth of storage in the liver.
Deficiency: Macrocytic, megaloblastic anemia; hypersegmented PMNs; paresthesias, subacute combined degeneration of dorsal columns, lateral corticospinal tracts, spinocerebellar tracts due to abnormal myelin. Increased homocysteine and MMA. From insufficient uptake, malabsorption, lack of IF, or absence of terminal ileum.
Vitamin C (ascorbic acid)
Function: antioxidant. Facilitates iron absorption. Necessary for hydroxylation of proline and lysine in collagen synthesis, and for dopamine b-hydroxylase (converts dopamine to NE). Found in fruits and veggies.
Deficiency = Scurvy: swollen gums, bruising, hemarthrosis, anemia, poor wound healing, perifollicular and subperiosteal hemorrhages, corkscrew hair, weakened immune response.
Excess: Nausea, vomiting, diarrhea, fatigue, calcium oxalate nephrolithiasis, increases risk of iron toxicity in predisposed individuals.
Vitamin D
Function: increases intestinal absorption of calcium and phosphate, increases bone mineralization
Deficiency: Rickets in kids (bone pain and deformity), osteomalacia in grown-ups (bone pain and muscle weakness), hypocalcemic tetany. From low sun exposure, malabsorption, liver failure, renal failure, prematurity.
Excess: Hypercalcemia, hypercalciuria, loss of appetite, stupor. Seen in sarcoidosis
Note: 25-OH D3 is the storage form, and calcitriol 1,25-(OH)2 D3 is the active form.
Vitamin E (tocopherol/tocotrienol)
Function: Antioxidant. Protects RBCs and membranes from free radical damage, enhances anticoagulant effects of warfarin.
Deficiency: Hemolytic anemia, acanthocytosis, muscle weakness, posterior column and spinocerebellar tract demyelination. Looks like B12 but without megaloblastic anemia, hypersegmented neutrophils, or increased MMA.
Vitamin K
Function: Cofactor for gamma-carboxylation of glutamic acid residues on various proteins for blood clotting (2, 7, 9, 10, Proteins C and S). Synthesized by intestinal flora.
Deficiency: Neonatal hemorrhage with high PT and PTT but normal bleeding time.
Zinc
Function: Essential for the activity of a whole bunch of enzymes. Important for formation of zinc fingers.
Deficiency: Delayed wound healing, hypogonadism, decreased adult hair, dysguesia (distorted taste), anosmia, acrodermatitis enteropathica. May predispose to alcoholic cirrhosis.
