Intrinsic factor (IF) is secreted by parietal cells of the stomach. In a patient post-total gastrectomy, which vitamin deficiency develops after 3–5 years, and through which ileal transporter is its IF-bound form absorbed?

• A Vitamin B12 deficiency; absorbed via PCFT (proton-coupled folate transporter) in proximal jejunum
• B Folate deficiency; absorbed via DPPIV-receptor in duodenum
• C Vitamin B12 deficiency; absorbed via cubilin-amnionless (CUBAM) receptor complex in terminal ileum ✓
• D Vitamin D deficiency; absorbed via VDR-mediated active transport in proximal jejunum

Explanation

Intrinsic factor, secreted by gastric parietal cells (same cells that secrete HCl), binds dietary vitamin B12 in the stomach and proximal duodenum, protecting it from proteolytic digestion. The IF-B12 complex travels to the terminal ileum, where it is recognised and absorbed via the CUBAM receptor complex (cubilin + amnionless protein) on enterocyte apical membranes. After total gastrectomy, absent IF leads to B12 malabsorption; megaloblastic anaemia and subacute combined degeneration of the spinal cord (SACD) develop after body stores (3–5 years) are depleted.

Reference: Guyton & Hall, Textbook of Medical Physiology, 14th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.