Antithrombin (AT) is a small protein molecule that aids in the inactivation of coagulation system enzymes. It's often used during surgical procedures in patients with low antithrombic levels, and it serves as a natural blood thinner. Antithrombin is a serine protease inhibitor with a structure similar to alpha 1-antichymotrypsin, alpha 2-antiplasmin, and heparin cofactor II....