A 62-year-old woman with autoimmune thyroiditis presents with fatigue, glossitis, and bilateral numbness in her hands and feet. Peripheral smear shows macrocytes and hypersegmented neutrophils. Anti-intrinsic factor antibodies are positive. Absorption of the deficient substance occurs primarily in which part of the gastrointestinal tract?
- A Duodenum
- B Jejunum
- C Terminal ileum ✓
- D Colon
Correct answer: C. Terminal ileum
Explanation
This patient has pernicious anemia from vitamin B12 deficiency. Vitamin B12 bound to intrinsic factor is absorbed specifically in the terminal ileum via cubilin receptors. The duodenum absorbs iron and calcium. The jejunum absorbs most other nutrients. The colon absorbs water and electrolytes, not vitamin B12.
Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.