16 Questions
What is the primary cause of vitamin B12 deficiency among vegetarians?
Dietary causes
What is the main manifestation of vitamin B12 deficiency known as pernicious anemia?
Megaloblastic anemia
What does B12 deficiency lead to, resulting in symptoms of megaloblastic anemia?
Impaired utilization of methyl-THF
What is the possible cause of hyperhomocysteinemia and homocystinuria in vitamin B12 deficiency?
Failure to metabolize homocysteine
What is the effect of B12 deficiency on the utilization of methyl-THF for the conversion of homocysteine to methionine?
It impairs the conversion process
Which form of cells is most affected by the deficiency of THF forms due to B12 deficiency?
Rapidly dividing cells such as erythropoietic cells
What is the primary cause of vitamin B12 deficiency known as pernicious anemia?
Autoimmune destruction of the gastric parietal cells
What is the effect of B12 deficiency on the utilization of methyl-THF for the conversion of homocysteine to methionine?
Impaired utilization leading to accumulation of methyl-THF
What is the main cause of hyperhomocysteinemia and homocystinuria in vitamin B12 deficiency?
Failure to metabolize homocysteine
What is the consequence of B12 deficiency on the THF forms needed in cell division?
Deficiency of the THF forms
What is the likely cause of megaloblastic anemia in vitamin B12 deficiency?
Impaired utilization and accumulation of methyl-THF
What is the main cause of vitamin B12 deficiency due to a decrease in intrinsic factor (IF)?
Autoimmune destruction of the gastric parietal cells
What is the rare cause of vitamin B12 deficiency, except among vegetarians?
Dietary causes
What is the primary manifestation of vitamin B12 deficiency known as pernicious anemia?
Megaloblastic anemia
What is the consequence of B12 deficiency on the utilization of methyl-THF for the conversion of homocysteine to methionine?
Impaired utilization of methyl-THF
What effect does B12 deficiency have on the THF forms needed in cell division?
Deficiency of THF forms
Study Notes
- Vitamin B12 deficiency causes: Malabsorption, Gastrectomy, Autoimmune destruction of gastric parietal cells (decrease of IF), Rare dietary deficiency among vegetarians
- Vitamin B12 deficiency symptoms: Pernicious anemia - Megaloblastic anemia (folate trap in methyl-THF form), Neurological manifestations, Hyperhomocysteinemia and homocystinuria, Methylmalonic aciduria
- Folate Trap Hypothesis: B12 deficiency impairs utilization of methyl-THF for homocysteine conversion, leading to a deficiency of THF forms needed in cell division, most notably in rapidly dividing cells like erythropoietic cells of bone marrow, causing megaloblastic anemia.
Test your knowledge on the causes and manifestations of vitamin B12 deficiency. Learn about malabsorption, gastrectomy, autoimmune destruction, and dietary causes as well as the manifestations such as pernicious anemia, neurological manifestations, hyperhomocysteinemia, and methylmalonic aciduria.
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