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What is Intrinsic Factor
Intrinsic Factor is produced in the stomach by what are known as the parietal cells. Intrinsic factor is a glycoprotein (
a protein that has a carbohydrate as the nonprotein component) which is absolutely essential for the absorption of Vitamin B12 in the small intestine, specifically the terminal ileum. When the vitamin B12 is in the acidic environment of the stomach (gastrum) it becomes bound to one of two B12 binding proteins present in the gastric juice. By the time Vitamin B12 reaches
the small intestine, it is in a less acidic environment, and the B12 binding proteins dissociate from the vitamin which then allows it to bind to Intrinsic Factor and enter the portal circulation (
blood veseels that conduct blood from the digestive organs, spleen, pancreas, and gallbladder to the liver)
through a receptor in the ileal mucosa that is specific for the resultant B12-Intrinsic Factor complex.
In the case of P ernicious Anemia, which is an autoimmune disease, special antibodies known as autoantibodies target the Intrinsic Factor or the parietal cells themselves, which leads to Intrinsic Factor deficiency that then results in the malabsorption of Vitamin B12 which ultimately results in Megaloblastic Anemia.
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