Tibolone: influence on markers of cardiovascular disease

Tibolone, a synthetic steroid with estrogenic, androgenic, and progestogenic properties relieves climacteric symptoms and prevents postmenopausal bone loss. The influence of tibolone treatment on coagulation, fibrinolysis, and lipid metabolism was investigated in 91 healthy late postmenopausal women. They were randomly assigned in a double-blind, placebo-controlled 2-year study to receive either tibolone 1.25 mg (n = 36, 29 completed) or 2.5 mg (n = 35, 28 completed) or placebo (n = 20, 13 completed). The biochemical markers of lipid metabolism, fibrinolysis, and coagulation were measured every 3 months. In both tibolone groups a similar (approximately 30%) decrease in high density lipoprotein cholesterol and a corresponding lowering of apolipoprotein A-1 (P < 0.001) was detected. Also serum total cholesterol and triglycerides were reduced (approximately 15%; P < 0.01), whereas low density lipoprotein cholesterol, apolipoprotein B, and lipoprotein(a) were unaffected by tibolone. The two dose levels of tibolone resulted in a similar, marked lowering (approximately 30%) of tissue plasminogen activator and plasminogen activator inhibitor activity as compared with placebo (P < 0.001). Plasminogen increased (approximately 15%; P < 0.001) in both groups. Fibrinogen was lowered (P < 0.01) in the low-dose group, and antithrombin III remained unchanged. The overall effect on hemostatic factors of the present doses of tibolone in healthy, late postmenopausal women tends towards increased fibrinolysis and unchanged coagulation. This may be beneficial and might theoretically counterbalance the potentially negative effect of the decrease in high density lipoprotein cholesterol.