Vitamin B12 deficiency causes: Difference between revisions
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* Hereditary causes such as severe [[MTHFR]] deficiency, [[homocystinuria]], and [[transcobalamin]] deficiency. | * Hereditary causes such as severe [[MTHFR]] deficiency, [[homocystinuria]], and [[transcobalamin]] deficiency. | ||
====Drug Side Effect==== | |||
* [[Metformin]], [[Glyburide and Metformin]] | |||
==References== | ==References== | ||
Revision as of 16:50, 16 October 2014
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Causes
- Inadequate dietary intake of vitamin B12. As the vitamin B12 occurs naturally only in animal products (eggs, meat, milk) a vegan diet can produce a deficiency unless one uses supplements or eats enriched food.[1]
- Selective impaired absorption of vitamin B12 due to intrinsic factor deficiency. This may depend on loss of gastric parietal cells in chronic atrophic gastritis (in which case, the resulting megaloblastic anaemia takes the name of "pernicious anaemia"), or on wide surgical resection of stomach (such as in bariatric surgery), or on rare hereditary causes of impaired synthesis of intrinsic factor. It takes years to develop deficiency after dietary absorption stops.
- Impaired absorption of vitamin B12 in the setting of a more generalized malabsorption or maldigestion syndrome. This includes any form of structural damage or wide surgical resection of the terminal ileum (the principal site of vitamin B12 absorption), forms of achlorhydria (including that artificially induced by drugs such as proton pump inhibitors), as well as bacterial overgrowth (such as in blind loop syndrome).
- Chronic intestinal infestation by the fish tapeworm Diphyllobothrium, that competes for vitamin B12, seizing it for its own use and therefore leaving insufficient amount for the host organism. This is mostly confined to Scandinavia and parts of Eastern Europe (for example, in preparers of gefilte fish, who would acquire the tapeworm by sneaking bits of uncooked fish while making the Eastern European delicacy, now eaten by Jews at Pesach).
- Hereditary causes such as severe MTHFR deficiency, homocystinuria, and transcobalamin deficiency.
Drug Side Effect
References
- ↑ Pernicious Anaemia Society - What is Pernicious Anaemia?, retrieved July 30, 2007.
- ↑ Ting R, Szeto C, Chan M, Ma K, Chow K (2006). "Risk factors of vitamin B(12) deficiency in patients receiving metformin". Arch Intern Med. 166 (18): 1975–9. PMID 17030830.