Which organ is the primary site of intrinsic factor production?

• A. Liver
• B. Stomach
• C. Small intestine
• D. Pancreas

Answer: (B)

Intrinsic factor is produced by the stomach, specifically by the gastric parietal cells in the fundus/body. These cells secrete intrinsic factor into the gastric lumen, where it binds vitamin B12 and protects it for absorption later in the terminal ileum. The liver and pancreas do not produce intrinsic factor, and while the small intestine is where the B12-intrinsic factor complex is absorbed, production occurs in the stomach. This connection explains why damage to gastric parietal cells can lead to impaired B12 absorption and pernicious anemia.