Thrombin is a key enzyme in the blood clotting system, belonging to the serine protease family. It is formed by the activation of the precursor protein prothrombin in the cascade reaction of blood coagulation. Primarily found in plasma, its function is to convert soluble fibrinogen into insoluble fibrin, thereby promoting clot formation. This process is central to blood coagulation and hemostasis, requiring the involvement of multiple clotting factors and cell surface receptors. The activity and expression of thrombin are tightly regulated to ensure a balance between clotting and anticoagulation. Genetic variations may lead to abnormalities in clotting function, such as excessive or inadequate clotting, thereby affecting thrombus formation or bleeding tendency.