TFPI (tissue factor pathway inhibitor) is a crucial anticoagulant protein that regulates blood coagulation through multiple mechanisms. Its primary function is to inhibit factor Xa directly and, in a factor Xa-dependent manner, inhibit the tissue factor/factor VIIa complex by forming a quaternary complex (TF-FVIIa-FXa-TFPI), effectively preventing further coagulation cascade activation 1. TFPI works synergistically with protein S to enhance factor Xa inhibition and is particularly important when activated protein C is present 2. The protein is predominantly expressed by megakaryocytes and microvascular endothelium under normal conditions, with endothelial cells providing anticoagulant activity through both surface-expressed heparin-like proteoglycans and TFPI 34. Beyond its classical anticoagulant role, TFPI has emerged as a regulator of erythropoiesis, where erythroblast-derived TFPI promotes heme biosynthesis in central macrophages through ERK1/2-GATA1 signaling 5. Clinically, TFPI deficiency presents therapeutic opportunities for hemophilia treatment, as TFPI inhibition can restore hemostasis through the extrinsic pathway without requiring factors VIII or IX 6. Additionally, TFPI demonstrates protective effects against atherosclerosis by inhibiting endothelial activation and vascular smooth muscle cell proliferation 7.