Antithrombin III: Physiology and clinical significance.

Antithrombin III is a very important natural anticoagulant. In combination with heparin, antithrombin III inhibits thrombin and other proteases of blood coagulation system. Normal concentration of antithrombin III in blood plasma ranges from 0.15 to 0.18 mg/ml. However, activity of antithrombin III should also be evaluated in addition to its concentration. There is both congenital and acquired deficiency of antithrombin III. A decrease in the level of antithrombin III is accompanied by an increase in the rate of thrombogenesis. Heparin therapy is ineffective in this case, because of catalytic role in the thrombin-antithrombin III-heparin system. Efficacy of therapy of the deficiency of antithrombin III depends on the character of the pathology, which caused this deficiency, However, the problem of correction of the level of antithrombin III and its activity requires further profound research.