What causes the deficiency of intrinsic factor leading to anemia?

The deficiency of intrinsic factor, which leads to anemia, is primarily due to the removal of part of the stomach. Intrinsic factor is a glycoprotein produced by the parietal cells of the stomach that is essential for the absorption of vitamin B12 in the intestines. Vitamin B12 is crucial for red blood cell production and DNA synthesis. If a portion of the stomach is surgically removed, such as in a gastrectomy, the production of intrinsic factor may be significantly decreased or eliminated, leading to an inability to absorb sufficient vitamin B12. This deficiency can result in a type of anemia known as pernicious anemia, characterized by macrocytic red blood cells due to inadequate vitamin B12 levels.

In contrast, chronic blood loss primarily results in iron deficiency anemia due to a lack of iron needed for hemoglobin synthesis. Malnutrition can contribute to various types of anemia but does not specifically target intrinsic factor. Vitamin D deficiency affects calcium metabolism and bone health but does not directly influence the production of intrinsic factor or the absorption of vitamin B12.