Does inflammation increase hepcidin and lock iron in storage, reducing absorption and mobilization?

Research consistently confirms that inflammation disrupts iron homeostasis by elevating hepcidin, a peptide hormone that acts as the "master regulator" of iron. This process creates a state of functional iron deficiency, where iron is present in the body but unavailable for use.

Clinical and Mechanistic Evidence

Inflammation, particularly driven by the cytokine interleukin-6 (IL-6), triggers the production of hepcidin in the liver. This occurs through the activation of the JAK/STAT3 signaling pathway, where IL-6 leads to the phosphorylation of STAT3, which then binds to the hepcidin promoter to increase its transcription.

Once elevated, hepcidin controls iron levels through several key actions:

• Intestinal Blockage: Hepcidin binds to ferroportin, the only known channel for iron to exit cells, on the surface of duodenal enterocytes (the cells lining the small intestine). This binding causes ferroportin to be internalized and destroyed (ubiquitinated and degraded in lysosomes), effectively blocking the absorption of dietary iron into the bloodstream.
• Iron Trapping: A similar process occurs in macrophages (which recycle iron from old red blood cells) and hepatocytes (storage cells). Hepcidin degrades their ferroportin channels, trapping iron inside these cells.
• Reduced Mobilization: Even if iron stores are high, the lack of functional ferroportin means iron cannot be released (mobilized) into the plasma. This leads to a drop in serum iron and low transferrin saturation, depriving the bone marrow of the iron needed for red blood cell production.

Safety and Clinical Implications

This "locking away" of iron is thought to be an evolutionary defense mechanism to starve invading pathogens of the iron they need to replicate. However, in the context of chronic inflammation, it leads to Anemia of Inflammation (or Anemia of Chronic Disease).

• Diagnostic Markers: In these cases, patients often show high ferritin (reflecting trapped storage iron) but low serum iron and low transferrin saturation, along with elevated inflammatory markers like C-reactive protein (CRP).
• Practical Impact: For individuals with inflammatory conditions, standard oral iron supplementation may be ineffective because high hepcidin levels prevent its absorption. In such cases, managing the underlying inflammation or using intravenous iron (which bypasses the intestinal block) may be necessary to improve iron status.

Bottom line

Inflammation increases hepcidin through the IL-6/STAT3 pathway, which degrades the iron exporter ferroportin. This dual action blocks intestinal absorption and traps iron in cellular stores, causing functional iron deficiency even when total body iron is sufficient.