Objective Growth hormone/insulin-like growth factor-1(GH/IGF-1) hypersecretion may influence risk factors contributing to the increased cardiovascular morbidity and mortality associated with acromegaly However, so far little is known about the impact of GH/IGF-1 on coagulation and fibrinolysis in acromegalic patients as possible risk factors for cardiovascular disease (CVD). To our knowledge, plasma tissue factor pathway inhibitor (TFPI) and thrombin-activatable fibrinolysis inhibitor (TAFI) levels in these patients have not been investigated. Therefore, the main purpose of this study was to evaluate the markers of endogenous coagulation/fibrinolysis, including TFPI and TAFI, and to investigate the relationships between GH/IGF-1 and these hemostatic parameters and serum lipid profile in patients with acromegaly. Research Methods and Procedures A total of 22 patients with active acromegaly and 22 age-matched healthy controls were included in the study. Fibrinogen, factors V, VII, VIII, IX, and X activities, von-Willebrand factor (vWF), antithrombin III (AT 111), protein C, protein S, tissue plasminogen activator (t-PA), tissue plasminogen activator inhibitor-1 (PAI-1), TFPI and TAFI, as well as common lipid variables, were measured. The relationships between serum GHAGF-1 and these hemostatic parameters were evaluated. Results Compared with the control subjects, fibrinogen, AT III, t-PA, and PAI-1 were increased significantly in patients with acromegaly (P < 0.000 1, P < 0.05, P < 0.01, and P < 0.000 1, respectively), whereas protein S activity and TFPI levels were decreased significantly (P < 0.05 and P < 0.01, respectively). Plasma TAFI Ag levels did not significantly change in patients with acromegaly compared with the controls. In patients with acromegaly, serum GH levels were inversely correlated with TFPI and apo AI levels (r: -0.514, P: 0.029 and r: -0.602, P: 0.014, respectively). There was also a negative correlation between insulin-like growth factor -1 (IGF-1) and PAI-1 (r: -0.455, P:0.045). Discussion We found some important differences in the hemostatic parameters between the patients with acromegaly and healthy controls. Increased fibrinogen, t-PA, PAI-1 and decreased protein S and TFPI in acromegalic patients may represent a potential hypercoagulable and hypofibrinolytic state, which might augment the risk for atherosclerotic and atherothrombotic complications. Thus, disturbances of the hemostatic system and dyslipidemia may contribute to the excess mortality due to CVD seen in patients with acromegaly.