Objective Although the strong association between hyperprolactinaemia and platelet aggregation is well recognized, there are no studies on changes in coagulation and fibrinolytic status in patients with prolactinoma. To our knowledge, tissue plasminogen activator inhibitor-1 (PAI-1), 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 prolactin (PRL) and these haemostatic parameters and serum lipid profile in patients with prolactinoma. Research methods and procedures Twenty-two patients with untreated, newly diagnosed prolactinoma and 20 age-matched healthy controls were included in the study. Platelet count, mean platelet volume, prothrombin time, activated partial thromboplastin time, fibrinogen, factors V, VII, VIII, IX and X activities, von Willebrand factor, antithrombin III (AT-III), protein C, protein S, tissue plasminogen activator (t-PA), PAI-1, TFPI and TAFI, as well as common lipid variables, were measured. The relationships between serum PRL and these haemostatic parameters were evaluated. Results Compared with the control subjects, total cholesterol, low density lipoprotein cholesterol, apolipoprotein B, platelet count, fibrinogen, AT-III, PAI-1 and PAI-1/t-PA ratio were significantly increased in patients with prolactinoma (P < 0 center dot 0001, P < 0 center dot 001, P < 0 center dot 05, P < 0 center dot 05, P < 0 center dot 0001, P < 0 center dot 05, P < 0 center dot 0001 and P < 0 center dot 0001, respectively), whereas TFPI levels were significantly decreased (P < 0 center dot 01). Plasma TAFI Ag levels were not significantly different in patients with prolactinoma compared with the controls. In patients with prolactinoma, serum PRL was positively correlated with plasma FVII levels and apo B (r: 0 center dot 679, P < 0 center dot 05; r: 0 center dot 548, P < 0 center dot 05, respectively). Conclusion We found some important differences in the haemostatic parameters between the patients with prolactinoma and healthy controls. Increased platelet count, fibrinogen, PAI-1 and decreased TFPI in patients with prolactinoma may represent a potential hypercoagulable and hypofibrinolytic state, which might augment the risk for atherosclerotic and atherothrombotic complications. Thus, disturbances of the haemostatic system and dyslipidaemia may lead to the excess mortality in patients with prolactinoma.