Iron Haemostasis

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  • Transferrin = glycoprotein to which absorbed iron in the bloodstream is bound to.  Each molecule binds two atoms of ferric iron.  Normally about 20-45% of binding sites are filled.  About 0.1% of total body iron is circulating in bound form to transferrin.

  • Each day 0.5 - 1.0 mg of iron is lost in the faeces, urine and sweat.  Loss of about 1- 2 mg of iron every day via desquamation of epithelium.  Menstruation, growth (0.6 mg) and pregnancy (1-2 mg per day)

  • Usually daily diet = 15-20 mg, roughly 10% absorbed

  • Ferritin is a water-soluble complex of iron and protein (iron + apoferritin) used for storage (2/3 about 1000 mg, in reticuloendothelial cells, hepatocytes and skeletal muscle cells.  Haemosiderin is an insoluble iron-protein complex found in macrophages in the BM, liver and spleen.  1/3 of stored iron (about 500 mg) stored as haemosiderin.

  • 2.5-3g of iron in circulation as Hb

  • TIBC = amount of iron that would appear in plasma if all the transferrin were saturated with iron