Intrinsic factor

Intrinsic factor is a glycoprotein secreted by stomach parietal cells that binds vitamin B12 and enables its absorption in the terminal ileum.

Vitamin B12: Vitamin B12 is a water-soluble vitamin required for DNA synthesis and normal nervous-system function. Intrinsic factor binds this vitamin and carries it to the site of absorption.
Pernicious anemia: An autoimmune disorder in which vitamin B12 deficiency impairs red blood cell production. Autoimmune loss of intrinsic factor commonly causes this form of B12-deficiency anemia.
Anti-intrinsic factor antibody: An autoantibody that binds intrinsic factor and can interfere with vitamin B12 absorption. Detecting it supports an autoimmune cause of intrinsic-factor failure.
Glycoprotein: A glycoprotein is a protein molecule bearing covalently attached carbohydrate chains. Intrinsic factor’s carbohydrate-bearing structure helps define its molecular form.
Food-cobalamin malabsorption: Food-cobalamin malabsorption is impaired release of vitamin B12 from food despite preserved absorption of free B12. Unlike intrinsic-factor deficiency, this disorder can leave the intrinsic-factor pathway intact.
Parietal cell: A gastric epithelial cell that secretes hydrochloric acid and intrinsic factor. These stomach cells produce and release intrinsic factor.
Autoimmune gastritis: Chronic immune-mediated inflammation that damages the stomach’s acid-secreting mucosa. Its destruction of parietal cells can reduce intrinsic factor secretion.
Vitamin B12 deficiency: A state in which the body lacks enough vitamin B12 for normal cellular and neurological function. Loss of intrinsic-factor-mediated uptake is a major cause of this deficiency.
Haptocorrin: Haptocorrin is a salivary and gastric protein that binds vitamin B12 in the upper digestive tract. It protects B12 before pancreatic enzymes release it for binding to intrinsic factor.
Ileal disease: Ileal disease is inflammation or damage affecting the final segment of the small intestine. It can prevent B12 uptake even when intrinsic factor binds the vitamin normally.

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