Iron is primarily absorbed in which region of the small intestine?

Iron is primarily absorbed in which region of the small intestine?

• A. Duodenum and Proximal Jejunum
• B. Stomach
• C. Colon
• D. Ileum

Answer: (A)

Iron is absorbed primarily in the duodenum and proximal jejunum. This early part of the small intestine has enterocytes equipped with the key machinery for intestinal iron uptake: for non-heme iron, ferric iron (Fe3+) is reduced to ferrous iron (Fe2+) by the brush-border enzyme Dcytb and then transported into the cell via DMT1. Inside the enterocyte, iron can be stored as ferritin or moved into the bloodstream through ferroportin, with hephaestin helping convert Fe2+ to the ferric form (Fe3+) for binding to transferrin. Heme iron from animal sources is absorbed through a somewhat different route but largely within the same proximal small-intestinal region. The upper small intestine is thus the main site of iron absorption; the ileum absorbs only limited iron, while the stomach and colon are not major sites of iron uptake. Regulation by hepcidin modulates ferroportin activity to match iron needs, further emphasizing the duodenum and proximal jejunum as the central stage for iron entry into the body.

Iron is absorbed primarily in the duodenum and proximal jejunum. This early part of the small intestine has enterocytes equipped with the key machinery for intestinal iron uptake: for non-heme iron, ferric iron (Fe3+) is reduced to ferrous iron (Fe2+) by the brush-border enzyme Dcytb and then transported into the cell via DMT1. Inside the enterocyte, iron can be stored as ferritin or moved into the bloodstream through ferroportin, with hephaestin helping convert Fe2+ to the ferric form (Fe3+) for binding to transferrin. Heme iron from animal sources is absorbed through a somewhat different route but largely within the same proximal small-intestinal region. The upper small intestine is thus the main site of iron absorption; the ileum absorbs only limited iron, while the stomach and colon are not major sites of iron uptake. Regulation by hepcidin modulates ferroportin activity to match iron needs, further emphasizing the duodenum and proximal jejunum as the central stage for iron entry into the body.