The use of tibolone dose decrease the concentration of the total cholesterol, triglicerides, HDL cholesterol, without a significant decrease of LDL cholesterol. Also, the use of tibolone does not have any significant effect on the concentrations of antitrombin III, fibrinogen and C-reactive proteine. The number of serum parameters measured in this study was limited, thus that was the reason to discuss only about the metabolism of lipids in the patients from the tibolone group. The final condusion about the risk for cardiovascular diseases in the patients on tibolone, howerer, reqnires were extensive further clinical exeminations.

Hemostatic system, as an integral part of biological homeostatic mechanism in humans, is subject to changes due to effect of hormonal therapy used in preparation for in vitro fertilization. The objective of the study was to analyze the impact of hormonal changes on homeostatic parameters during four cycles of preparation, according to long-term protocol for in vitro fertilization. The following parameters were determined in the study: prothrombin time, activated partial thromboplastin time, fibrinogen, antithrombin III, plasminogen, a2-antiplasmin and plasminogen activator inhibitor. In the period of ovarian hyperstimulation and in postovulatory period, significantly lower PT, APTT, AT III, PAI-1 and a2-APL values were obtained (p<0.05), while fibrinogen concentration was significantly higher (p<0.05), in relation to the first two periods. PLG activity was significantly decreased in postovulatory period in relation to former three periods (p<0.05). Data obtained by Pearson?s correlation analysis show that there is significant negative correlation in postovulatory period between PLG and a2APL, as well as between APTT and PAI-1 (Rp>0.404, for p<0.05). These changes are manifested as more pronounced procoagulant forms, which are suppressed by simultaneous activation of fibrinolytic system as the opposite response, what keeps the balance in homeostatic system and prevents the development of adverse thrombotic complications.