Hepcidin

The Hepcidin-Ferroportin Axis#

Hepcidin binds ferroportin on the surface of enterocytes, macrophages, and hepatocytes, triggering its internalization and degradation.^{[1]Mechanism of Iron Ion Homeostasis in Intestinal Immunity and Gut Microbiota RemodelingHonghong Bao, Yi Wang, Hanlin Xiong et al. · 2024Open reference 1 ↓}

When hepcidin is high: ferroportin is destroyed, iron is trapped inside cells, serum iron falls. When hepcidin is low: ferroportin is expressed, iron flows into plasma from dietary absorption and macrophage recycling.

Regulation#

Iron excess upregulates hepcidin via the BMP-SMAD pathway (bone morphogenetic protein signaling). Metal-Driven Inflammation upregulates hepcidin via IL-6/JAK-STAT3 signaling—this is the basis of anemia of chronic disease. Iron deficiency and erythropoietic demand suppress hepcidin to increase iron availability.

Hypoxia suppresses hepcidin via HIF signaling.

The Iron Supplementation Paradox#

In inflammatory states (IBD, chronic infection, autoimmune disease), hepcidin is elevated and serum iron/ferritin may appear low. Clinicians interpret low iron markers as deficiency and prescribe iron supplementation.

However, high hepcidin means supplemental iron is poorly absorbed (blocked at the enterocyte) and what IS absorbed may feed iron-requiring pathogens rather than reaching the host's erythroid compartment.

Unabsorbed oral iron reaches the colon, where it feeds siderophore-producing Enterobacteriaceae and disrupts the Gut Microbiome.^{[1]Mechanism of Iron Ion Homeostasis in Intestinal Immunity and Gut Microbiota RemodelingHonghong Bao, Yi Wang, Hanlin Xiong et al. · 2024Open reference 1 ↓}

Infection Context#

Hepcidin elevation during infection is part of a coordinated host defense that includes Lactoferrin (iron sequestration at mucosal surfaces), ferritin (intracellular iron storage), and transferrin (limiting free plasma iron).

Vaginal lactoferrin concentrations positively correlate with serum hepcidin levels, suggesting coordinated systemic and mucosal iron restriction during infection.^{[2]Mucosal lactoferrin response to genital tract infections is associated with iron and nutritional biomarkers in young Burkinabe womenRoberts SA, Brabin L, Diallo S et al. · 2019Open reference 2 ↓}

Chronic Kidney Disease#

Hepcidin accumulates in CKD due to reduced renal clearance and chronic inflammation, contributing to the anemia of CKD and functional iron deficiency.^{[3]Molecular Mechanisms of Cellular Injury and Role of Toxic Heavy Metals in Chronic Kidney DiseaseManish Mishra, Larry Nichols, Aditi A. Dave et al. · 2022Open reference 3 ↓}

Iron supplementation in CKD patients with elevated hepcidin may be ineffective or harmful.