heparin / antithrombin system

Last reviewed 01/2018

Antithrombin is a serine protease inhibitor which inhibits the following coagulation factors:

  • thrombin
  • factor Xa
  • factors XIIa, XIIIa and IXa

Binding of heparin to antithrombin improves the speed with which antithrombin can neutralise these prothrombotic factors. In vivo, glycosaminoglycans on the endothelial cells serve as the endogenous catalysts for antithrombin activation.

Antithrombin deficiency is a cause of thrombophilia.

Heparin cofactor II is a distinct serine protease inhibitor which inhibits thrombin in the presence of heparin. Deficiency of heparin cofactor II may cause thrombophilia.