Body iron can be divided into two categories: storage iron and functional iron. Storage iron is that which is stored in the liver, spleen, and bone marrow; functional iron is that found in hemoglobin, myoglobin, and the iron-requiring enzymes Of the body. Storage iron represents the balance between

the amount Of iron taken in or recycled and the amount Of iron ost each day. n the United States, males typically have 1000 mg of stored iron while females have 300 mg. Iron can be stored as either ferritin Or hemosiderin. One Can estimate the amount Of sto ed iron by measuring Serum ferritin concentrations. Ferritin Ferritin is a protein that binds iron and stores it within the cells, especially in the liver. A small amount Of ferritin circulates 'n the b ood. Since circulating ferritin reflects the amount Of stored iron within the body, measurement of serum ferritin can be used to estimate iron stores. To estimate iron stores using serum ferritin concentrations, assume that I ferritin per liter B mg stored iron- Hemosiderin Hemoslderin is an Insolub e form Of stored iron that forms large concentrated clusters With n the Soluble Transferrin Receptor The measurement Of soluble serum transferrin receptor (STfR) has recently been proposed as a new sensitive indicator of iron deficiency. The sTiR is an iron-related protein that regulates the uptake of iron into body cells- When the cells need more iron, the