18 terms

Vitamins

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Vitamin A (retinol)
Function:
- antioxidant
- retinal pigment constituent
- tx of APL (M3 variant of AML) and measles
- found naturally in liver and leafy vegetables

Deficiency (malabsorption, nutritional):
- night blindness
- dry skin
- impaired immunity

Excess:
- arthralgias
- fatigue
- inc ICP -> headaches / pseudotumor cerebri
- sore throat
- alopecia

* teratogen: cleft palate, cardiac abnormalities
- pregnancy test before rx isotretinoin for severe acne
Vitamin B1 (thiamine)
Function: complexed as thiamine pyrophosphate (TPP) as a cofactor for several enzymes

Common in alcoholics or pts with wt loss surgery

Deficiency:
- Beriberi (polyneuritis, dilated cardiomyopathy, high-output CHF, edema)
Ber1-Ber1 = Beriberi
- dry: symmetrical polyneuritis, symmetrical muscle wasting
- wet: high-output cardiac failure -> dilated cardiomyopathy, edema


- Wernicke-Korsakoff syndrome (confusion, ophthalmoplegia, ataxia + confabulation, personality change, permanent memory loss)
* due to damage of medial dorsal nucleus of thalamus and mamillary bodies
Vitamin B2 (riboflavin)
Function: cofactor in oxidation and reduction (eg FADH2); FMN and FAD are derived from riboFlavin
- uncommon in industrialized nations but documented in regions of the world with severe food shortages

Deficiency:
- photophobia
- angular stomatitis
- cheilosis (lip inflammation, scaling/fissure at mouth corners)
- corneal vascularization
- sore throat/pharyngitis
- hyperemic and edematous oropharyngeal mucous membranes
- glossitis
- normocytic-normochromic anemia
- seborrheic dermatitis (often of the genital area)
Vitamin B3 (niacin)
Function:
- derived from tryptophan; requires vit B6 for synthesis
- constituent of NAD+ and NADP+
* may be used for tx of hypercholesterolemia

Deficiency:
- pellagra (4 D's = diarrhea, dermatitis, dementia, death)
* dermatitis is bilateral and symmetric in sun exposed areas and resembles a sunburn (eventually becomes hyperpigmented and thickened)
* "dementia" can range from poor concentration, irritability, aggressiveness, and dementia
* can be caused by Hartnup dz (dec tryptophan absorption), malignant carcinoid synd (inc tryptophan metabolism), or INH (dec vit B6)
- glossitis (beefy, red tongue)

Excess:
- facial flushing
Vitamin B5 (pantothenate)
Function: component of CoA and fatty acid synthase (pantothen-A : Co-A)

Deficiency:
- dermatitis
- enteritis
- alopecia
- adrenal insufficiency
Vitamin B6 (pyridoxine)
Function:
- required for synthesis of niacin (vit B3 tryptophan)
- cofactor for cellular processes (eg transamination)

Deficiency:
- convulsions
- hyperirritability
- depression
- dermatitis
- stomatitis
- peripheral neuropathy (INH injection; OCPs)
- sideroblastic anemias
- inc homocysteine = risk factor for venous thromboembolic dz and atherosclerosis

* Required during INH doses
Vitamin B12 (cobalamin)
Function
- absorption requires intrinsic factor
- cofactor for homocysteine methyltransferase and methylmalonyl-CoA mutase

Dx: Schilling test

Deficiency:
- macrocytic, megaloblastic anemia with neurological symptoms (optic neuropathy, subacute combined degeneration, paresthesia)
* due to abnormal myelin
- glossitis

* Deficiency caused by:
Malabsorption (sprue, enteritis, Diphyllobothrium latum)
Lack of IF (pernicious anemia, gastric bypass)
Absence of terminal ileum (Crohn's dz)
Vitamin C (ascorbic acid)
Function:
- antioxidant
- facilitates iron absorption
- collagen synthesis
- dopamine -> norepinephrine synthesis

Deficiency:
- impaired collagen synthesis and damaged collaged tissue
- scurvy (swollen gums, bruising, anemia, poor wound healing)
- weakened immune response
- ecchymosis, petechiae, bleeding gums, hyperkeratosis, Sjogren's syndrome, arthralgias
- systemic: weakness, edema, malaise, joint swelling/pain, coiled hair, depression, neuropathy, vasomotor instability

Excess:
- calcium oxalate nephrolithiasis
Vitamin D
- D2: ergocalciferol - ingested from plants
- D3: cholecalciferol - consumed in milk; formed in sun-exposed skin

storage form 25-OH D3 converted by 1-alpha-hydroxylase from kidney to active form 1,25-(OH)2 D3 aka calcitriol

Function:
- inc intestinal absorption of calcium and phosphate
- inc bone resorption

Deficiency:
- rickets in children (bending bones)
- osteomalacia in adults (soft bones)
- hypocalcemic tetany

Excess: (seen in sarcoid -> inc activation of vit D by epitheloid macrophages)
- hypercalcemia
- hypercalciuria
- stupor
Vitamin E
E is for Erythrocyte

Function:
- protects erythrocytes and membranes and membranes from free-radical damage

Deficiency:
- inc fragility of erythrocytes -> hemolytic anemia
- muscle weakness
- posterior column and spinocerebellar tract demyelination
Vitamin K
Synthesized by intestinal flora (deficiency can be cause by prolonged Ab use)

Function: catalyzes gamma-carboxylation of glutamic acid on clotting factors II, VII, IX, X, and protein C and S
"K is for Koagulation"

Deficiency:
- neonatal hemorrhage (sterile intestines)
* neonates given vit K injection at birth
- inc PT and PTT but normal BT

Warfarin (Coumadin) is a Vit K antagonist
Vitamin B7 (Biotin)
Function: cofactor for carboxylation enzymes

Deficiency:
- dermatitis
- enteritis
- alopecia

* Can be caused by ingestion of raw eggs or antibiotic use
- raw eggs have Avidin -> Avidin binds Biotin -> deficiency
"AVIDin is in raw egg whites -> AVIDly binds biotin"
Folic acid
MOST COMMON vitamin deficiency in US
- small reserves in liver
- acquired from green leafy vegetables

Function: converted to tetrahydrofolate (THF), a coenzyme important for synthesis of nitrogenous bases in DNA and RNA

Deficiency:
- sprue
- macrocytic, megaloblastic anemia w/o neurological symptoms

* Deficiency can be caused by drugs
- phenytoin
- sulfonamides
- MTX
Magnesium
Deficiency:
- weakness
- muscle cramps
- exacerbations of hypocalcemic tetany
- CNS hyperirritability leading to tremors
- choreoathetoid movement
Selenium
Deficiency:
- Keshan dz (cardiomyopathy)
- deficiency due to chronic TPN, malabsorption, or malnutrition
What are the fat soluble vitamins?
ADEK - fat soluble: absorption dependent on gut (ileum) and pancreas

* Toxicities more common than water-soluble vitamins bc fat soluble vitamins can accumulate in fat
* Malabsorption syndrome (steatorrhea) eg CF and sprue, or mineral oil intake can cause fat-soluble vitamin deficiencies

Vit A (retinol)- Vision

Vit D - Bone calcification; Ca homeostasis

Vit E - Antioxidant

Vit K - Clotting factors
What are the water soluble vitamins?
BCF - water soluble: all wash out easily from body except B12 and folate (stored in liver)

* B-complex deficiencies often result in triad: dermatitis, glossitis, diarrhea

Vit B1 (thiamine; TPP)

Vit B2 (riboflavin; FAD, FMN)

Vit B3 (niacin; NAD)

Vit B5 (pantothenic acid; CoA)

Vit B6 (pyridoxine; PLP)

Vit B7 (Biotin)

Vit B12 (cobalamin)

Vit C (ascorbic acid)

Folate
Zinc
Function: cofactor for many enzymes and transcription factor motif aka zinc fingers
- found in animal products, whole grains, bean, nuts
- digested primarily in jejenum

Deficiency:
- delayed wound healing
- dec adult hair/alopecia
- dysgeusia/abnormal taste
- anosmia
- bullous, pustulous lesions surrounding body orifices and/or extremities
- may predispose to alcoholic cirrhosis
- children: growth retardation