Intrinsic factor

Intrinsic Factor

Illustration showing the role of intrinsic factor in vitamin B12 absorption.

Intrinsic factor is a glycoprotein produced by the parietal cells of the stomach. It is essential for the absorption of vitamin B12 (cobalamin) in the small intestine, specifically in the ileum, not the large intestine as often mistakenly thought.

Function

The primary function of intrinsic factor is to:

• Bind to vitamin B12 in the stomach.
• Facilitate the transportation of vitamin B12 through the small intestine.
• Enable the absorption of vitamin B12 in the ileum, the last part of the small intestine.

Importance

Intrinsic factor is crucial for:

• The prevention of vitamin B12 deficiency, which can lead to pernicious anemia and neurological disorders.
• Supporting normal brain function, blood cell formation, and DNA synthesis through the absorption of vitamin B12.

Production

Intrinsic factor is produced by:

• Parietal cells, also known as oxyntic cells, located in the gastric glands of the stomach's lining.

Clinical Significance

Vitamin B12 Absorption

In the absence of intrinsic factor, vitamin B12 cannot be effectively absorbed, leading to deficiency conditions.

Pernicious Anemia

Pernicious anemia, a type of megaloblastic anemia, arises due to the lack of intrinsic factor, often as a result of an autoimmune response against parietal cells.

Diagnostic Use

Measurements of intrinsic factor antibodies are used to diagnose pernicious anemia and other conditions related to B12 malabsorption.

Treatment

For individuals lacking intrinsic factor, vitamin B12 deficiency is typically treated with:

• High-dose oral vitamin B12 supplements.
• Vitamin B12 injections, which bypass the need for intrinsic factor.

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