A 60-year-old man with a 6-month history of fatigue has megaloblastic anemia after subtotal gastrectomy. The most likely cause is absence of which gastric cell type?

A 60-year-old man with a 6-month history of fatigue has megaloblastic anemia after subtotal gastrectomy. The most likely cause is absence of which gastric cell type?

• A. Chief cells
• B. G cells
• C. Cardiac glands
• D. Parietal cells

Answer: (D)

Missing intrinsic factor from parietal cells leads to vitamin B12 deficiency, which causes megaloblastic (macrocytic) anemia. Parietal cells in the stomach secrete intrinsic factor, a protein essential for vitamin B12 absorption in the terminal ileum. When a subtotal gastrectomy removes many parietal cells, intrinsic factor production drops, B12 cannot be efficiently absorbed, and DNA synthesis in hematopoietic cells is impaired, producing megaloblastic anemia with fatigue over months. Chief cells make pepsinogen, not involved in B12 absorption; cardiac glands secrete mucus, and G cells secrete gastrin, neither of which directly impact intrinsic factor or B12 uptake.

Missing intrinsic factor from parietal cells leads to vitamin B12 deficiency, which causes megaloblastic (macrocytic) anemia. Parietal cells in the stomach secrete intrinsic factor, a protein essential for vitamin B12 absorption in the terminal ileum. When a subtotal gastrectomy removes many parietal cells, intrinsic factor production drops, B12 cannot be efficiently absorbed, and DNA synthesis in hematopoietic cells is impaired, producing megaloblastic anemia with fatigue over months. Chief cells make pepsinogen, not involved in B12 absorption; cardiac glands secrete mucus, and G cells secrete gastrin, neither of which directly impact intrinsic factor or B12 uptake.