[Hyperhomocysteinemia and the disturbance of haemostasis--facts and mythes].

The elevated concentration of homocysteine--Hcys (hyperhomocysteinemia) has been correlated with different pathologists, such as cardiovascular diseases. In the article, the some pathways of homocysteine metabolism (i.e. remethylation to methionine, formation of homocysteine thiolactone, and its enzymatic hydrolysis) and the actions of homocysteine and its metabolite--cyclic thioester--homocysteine thiolactone (HTL) on complex process of haemostasis, which regulates the flowing properties of blood, are described. Possible interaction of Hcys and HTL with endothelial cells, blood platelets, plasmatic fibrinogen and other coagulation factors, as the important major components of haemostasis are also discussed. The modification of haemostatic proteins (N-homocysteinylated or S-homocysteinylated proteins) induced by Hcys or its thiolactone, seem to be the main reason of biotoxicity of homocysteine in the disturbance of haemostasis and cardiovascular diseases.