DO LOWERED FACTOR-VII LEVELS AT EXTREMELY HIGH ENDOGENOUS ESTRADIOL LEVELS PROTECT AGAINST THROMBIN FORMATION

The purpose of the study was to find a model to study the effect of en dogenous oestradiol on haemostasis. Hormones and haemostatic variables were therefore measured before and after in vitro fertilization and e gg replacement therapy in 14 women with tubal infertility. The differe nces between the levels of the haemostatic variables at minimum and ma ximum levels of oestradiol and progesterone were evaluated. A signific ant increase in the plasma levels of coagulation factor VIII, von Will ebrand factor and fibrinogen was found between samples drawn before st imulation and at the highest oestradiol levels (P < 0.002, P < 0.002 a nd P < 0.015, respectively). However, coagulation factor VII activity and antigen decreased significantly (P < 0.001 and P = 0.009, respecti vely). The levels of the coagulation inhibitors protein C and antithro mbin decreased (P < 0.003 and P = 0.008, respectively), while that of free protein S increased (P = 0.039). No significant changes were obse rved in the fibrinolytic variables or in those reflecting thrombin act ivity (prothrombin fragment 1 + 2, thrombin-antithrombin complexes, so luble fibrin and D-dimers). In conclusion, the increase in the levels of factor VIII, von Willebrand factor, fibrinogen and the decrease in the levels of antithrombin and protein C may, if coagulation is trigge red, contribute to a hypercoagulable state. The depressed factor VII l evels and the tendency to elevated free protein S levels may constitut e a protective mechanism that modulates the coagulation system when le vels of oestradiol become extremely high.