Vitamin B12
Called extrinsic factor/ Cobalamin/ Cyanocobalamin
Need to formed RBC cells and DNA.
Functioning and development of brain and nerve.
Cures pernicious anemia
Active forms of Vitamin B12;
a. Methylcobalamin
b. Adenosyl Cobalamin
Absorption
Absorption of vitamin B12 requires the presence of intrinsic factor (secreted by parietal cells in stomach), absorption from small intestine.
Recommended daily allowance
Age RDA (in mcg)
1-3 years 0.9mcg
4-8years 1.2mcg
9-13 years 1.8mcg
14 and above 2.4 mcg
Pregnancy and lactation 2.8mcg
Causes of vitamin B12 deficiency
1. Low intestinal B12 uptake
2. Low intrinsic factor in stomach
3. Impaired absorption of vitamin B12 due to deficiency of HCL in gastric juice.
4. Inadequate dietary intake vitamin B12 .
5. Impaired absorption B12;
Structural damage
Surgical resection of ileum.
6. Surgical removal of small bowel (such as crohn's disease; Chronic inflammatory bowel disease), ileitis.
7. Hereditary;
Homocystinuria; body can't process amino acid methionine (unable to breakdown a protein from food are).
High homocysteine level indicate vitamin B12 or folate deficiency.
Transcobalamin deficiency; impairs the transport of cobalamin.
(Haptocorrin (HC)/ R-protein/R-factor; glycoprotein produced by the salivary glands)
Clinical manifestation of Vitamin B12 deficiency
1. Pernicious anaemia/ Addison's anaemia
Anaemia with bone marrow promegaloblastosis (megablasic anaemia)
Gastrointestinal symptoms
Neurological symptoms;
Numbness
Tingling of extremities
Irritability
Confusion
Sensory or motor deficiency (absent reflexes).
Degeneration of spinal cord
Impaired perception of touch and pressure
Ataxia of deep muscle tendon reflux
Psychological symptoms;
Fatigue/ depression/ poor memory
Other symptoms include;
Paleness/weakness/ shortness of breath/ difficulty in feeding.
Diagnostic Evaluation
1. Serum B12 level is low
2. Routine monitoring of methyl malonic acid level in urine.
3. Schilling test (vitamin B12 absorption test)
4. CNS damage suspected, vitamin B12 analysis in CSF done.
Management
Supplements in form of oral pills, sublingual, liquid or intranasal spray.
Transdermal patch supplement inform of;
Cyanocobalamin
Hydroxycobalamin
Methylcobalamin
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