Antithrombin iii

Antithrombin III (also known as AT III) is a non-vitamin K-dependent protease that inhibits coagulation by lysing thrombin and factor Xa. It is a small protein molecule that inactivates several enzymes of the coagulation system. Antithrombin III is located on chromosome 1q23-q25.1 and it belongs to the serpin family.

Function

Antithrombin III is a major inhibitor of thrombin. It also inhibits other activated serine proteases of the coagulation system, including factors IXa, Xa, XIa, and XIIa, as well as plasmin. Its inhibitory activity is greatly enhanced in the presence of heparin.

Clinical significance

Deficiency of antithrombin III can lead to an increased risk of thrombosis, the formation of abnormal blood clots in blood vessels. This can cause serious health problems such as deep vein thrombosis (DVT) and pulmonary embolism (PE). Antithrombin III deficiency can be inherited or acquired. Inherited deficiency is an autosomal dominant disorder, while acquired deficiency can occur due to liver disease, nephrotic syndrome, or disseminated intravascular coagulation (DIC).

Measurement

The level of antithrombin III in the blood can be measured with a laboratory test. This test is used to help diagnose a suspected antithrombin III deficiency and to monitor the effects of heparin therapy.

Treatment

Treatment for antithrombin III deficiency may include anticoagulant medications, such as warfarin, to prevent thrombosis. In severe cases, antithrombin III concentrate may be given.

See also

• Coagulation
• Thrombosis
• Deep vein thrombosis
• Pulmonary embolism