The total iron content of the body is about 3-3.5 g. From this, ~ 2.5 g is contained in red blood cells and their precursors in the bone marrow. The prosthetic group in hemoglobin is made up of complex iron-protoporphyrin (heme) in which the centrally located iron atom acts as a stabilizer of oxyhemoglobin.

Numerous enzymes and coenzymes require iron: peroxidase, catalase, cytochromes, many of Krebs cycle enzymes, monoamine oxidase.

Ingested iron is absorbed mainly in the intestinal tract and is stored temporarily in the form of Fe3 + enterocytes –ferritin , a complex of ferric hydroxide, ferric phosphate attached to the  apo-ferritin protein. Depending on the needs of the body iron is released into the bloodstream where it is transported in the form of Fe 3+ bound to plasma protein that at physiological pH which shows a high affinity for iron.

All transferrin molecule has two sites for iron bonding. Normally, only one third of the transferrin binding sites are occupied. Additional amount of iron that can be linked to transferrin is called latent ability or unsaturated iron binding (UIBC unsaturated iron-binding capacity =), and the amount of serum iron and UIBC value is

Indications for CTLF determination (in combination with serum iron and ferritin):

• Differential diagnosis of anemia, especially microcytic and / or hypochromic

• Evaluation of iron deficiency anemia, thalassemia, sideroblastic anemia

• The diagnosis of iron overload and hemochromatosis

• chronic inflammatory diseases,

 •malignancies,

 • haemochromatosis

 • liver cirrhosis,

• kidney disease

• thalassemia

 • hypoproteinemia (malnutrition, burns),

• hyperthyroidism.