What is intrinsic factor?
Intrinsic factor is a protein produced by a type of specialized cells that line the stomach wall known as parietal cells. During digestion, stomach acids release vitamin B12 from food and bind to intrinsic factor to form a complex. The formation of this complex is necessary for the absorption of vitamin B12 in the small intestine.
Why is Vitamin B12 so important?
Among having functional roles in the brain and nervous system, vitamin B12 is important in the production of red blood cells. Without sufficient intrinsic factor, vitamin B12 goes largely unabsorbed and the body cannot produce enough normal red blood cells, leading to anemia. Besides anemia, decrease in the numbers of neutrophils and platelets (neutropenia, thrombocytopenia) may also occur.
Anemia that is due to a lack of intrinsic factor:
Anemia that is due to a lack of intrinsic factor is called pernicious anemia. This is primarily an autoimmune condition that occurs when the body's immune system targets its own tissues and develops antibodies directed against the parietal cells and/or the intrinsic factor. These antibodies can damage the parietal cells and disrupt intrinsic factor production or prevent intrinsic factor from carrying out its biological function.
A high test result indicates the presence of circulating autoantibodies to intrinsic factor.
- If you have megaloblastic anemia, a low serum vitamin B12, and the presence of serum intrinsic factor antibodies it strongly supports the diagnosis of pernicious anemia.
- Positive factor antibodies test results are also observed in some patients with other autoimmune disorders such as autoimmune thyroid disease and rheumatoid arthritis. These people may be at risk for developing pernicious anemia at a later date.
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