Absorbed in the duodenum: heme iron directly; non-heme Fe²⁺ via DMT1 (vitamin C helps). Ferroportin exports it; transferrin carries it; ferritin stores it.
Hepcidin (liver) blocks ferroportin → iron stays in enterocytes and macrophages
Duodenal bypass → iron deficiency
Causes of iron deficiency
by age
Infants and toddlers: diet, cow's milk · children: growth · women: menses, pregnancy · older adults: GI bleeding · anyone: malabsorption.
Developing world: hookworm (Ancylostoma, Necator)
Celiac disease, gastrectomy, H pylori
Stages of iron loss
sequence
Stores fall → serum iron falls → normocytic anemia → microcytic, hypochromic anemia.
↓ ferritin first, ↑ TIBC, then ↓ iron and % saturation
Ferritin is the earliest and most specific marker
Fatigue, pica (ice — pagophagia), koilonychia (spoon nails), glossitis, angular cheilitis, restless legs.
Iron-dependent epithelial enzymes
Plummer-Vinson: esophageal web + iron deficiency + glossitis → SCC risk
Microcytic, hypochromic cells (wide central pallor), pencil cells; ↑ RDW.
↑ free erythrocyte protoporphyrin; reactive thrombocytosis
High platelets with microcytic anemia
Oral ferrous sulfate (with vitamin C); IV iron for malabsorption or intolerance.
Retic rises within 1 week
Side effects: constipation, black stool
Anemia of chronic disease
inflammation
Chronic infection, autoimmune disease (RA, SLE), malignancy.
IL-6 → hepcidin ↑ → iron trapped in macrophages, ↓ absorption; blunted EPO response
Normocytic, becomes microcytic; treat the disease
Kidneys make too little erythropoietin; often mixed with ACD and iron deficiency.
↓ EPO
Normocytic · erythropoiesis-stimulating agents + iron