Heparin Cofactor II Quick Facts
- Molecular mass: 65 000 D
- Synthesis: Liver
- Plasma concentration: 80mg/l, 1.2μmol/l
- Normal range: 60 – 170%
Biochemistry of Heparin Cofactor II
Heparin Cofactor II (HC II) is a specific thrombin inhibitor and, in contrast to antithrombin, does not inhibit factor Xa. HC II can thus influence antithrombin assays using thrombin. In contrast, test methods in which factor Xa is used, specifically determine the antithrombin activity, the complex formation between HC II and thrombin is considerably accelerated by heparin and dermatan sulphate. In vivo, HCII becomes active only when the antithrombin concentration has decreased below 30%. It seems likely that HC II is of significance as a thrombin inhibitor in the extra vascular area following injury. This is supported by the increased inhibition through dermatan sulphate, which is only found in the extra vascular space.
Clinical significance of Heparin Cofactor II
Hereditary heparin cofactor II deficiency correlates with increased risk for thrombosis. An acquired deficiency is observed in liver disease, diabetes mellitus and in DIC. Increased heparin cofactor II concentrations have been detected following use of oral contraceptives, during pregnancy and with increasing age.
Clinical or Research use of Heparin Cofactor II
- Suspected heparin cofactor II deficiency
- Diagnosis of thrombotic risk factors
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