Can inflammation raise hepcidin and trap iron in storage, causing low serum iron with normal or high ferritin?

Inflammation significantly alters iron metabolism, creating a profile distinct from simple nutritional deficiency. This process is driven by the body's acute-phase response, which prioritizes iron sequestration over availability for erythropoiesis.

Clinical and diagnostic evidence

During inflammatory states, diagnostic markers often diverge from typical iron-deficiency patterns. Evidence consistently shows that while serum iron and transferrin saturation (TSAT < 20%) fall, serum ferritin levels remain normal or become significantly elevated (often >100 μg/L). This phenomenon is termed "functional iron deficiency" or anemia of inflammation. Unlike absolute iron deficiency, where ferritin is typically <30 μg/L, inflammation-induced sequestration masks iron stores, making ferritin a less reliable marker of total body iron.

Mechanistic explanations

The primary driver of this metabolic shift is the hormone hepcidin, which functions as the master regulator of systemic iron homeostasis.

• Induction: Pro-inflammatory cytokines, specifically Interleukin-6 (IL-6), stimulate the liver to overproduce hepcidin through the IL-6/JAK/STAT3 signaling pathway.
• The Hepcidin-Ferroportin Axis: Hepcidin binds to and degrades ferroportin, the only known cellular iron exporter.
• Iron Sequestration: By removing ferroportin from cell membranes, hepcidin blocks dietary iron absorption in the duodenum and prevents macrophages from releasing iron recycled from old red blood cells.
• Storage Dynamics: Iron becomes trapped within the reticuloendothelial system (spleen and liver). Because ferritin is also an acute-phase reactant, its levels rise both as a storage response and as a direct result of inflammatory signaling.

Clinical implications

For practitioners and patients, identifying this pattern is critical for distinguishing between absolute iron deficiency (low stores) and anemia of chronic disease (trapped stores). Treatment focuses on managing the underlying inflammation to lower hepcidin levels, rather than simple oral iron supplementation, which may be poorly absorbed due to the hepcidin-induced blockade of intestinal transporters.

Bottom line

Inflammation triggers a hepcidin-mediated blockade of the iron exporter ferroportin, leading to low serum iron despite normal or high ferritin levels. This mechanism effectively "locks" iron in storage sites, making it unavailable for red blood cell production.