Hormone replacement therapy and hemostasis: principles of a complex interaction.

Postmenopausal women on hormone replacement therapy (HRT) have been shown to be at reduced risk of arterial thrombotic disease. The risk of venous thrombosis appears not to be increased in HRT users in the absence of specific risk factors. However, while these data refer predominantly to women using conjugated equine estrogens, it is less clear whether the favourable impact on cardiovascular diseases may also be achieved by other preparations. Dose, as well as route of application and, particularly, the combination of steroids have been shown to affect both the clinical and the metabolic profile. With regard to cardiovascular diseases, differential effects on the hemostatic system are of particular interest. The principles of the interaction of steroids with the hemostatic system are reviewed. Also, the principal limitations of the assessment of the hemostatic system, as well as its interpretation, with regard to cardiovascular diseases are discussed. It is proposed to view the hemostatic system predominantly as a monitor of endothelial function rather than as a mediator of potential harmful effects on the cardiovascular system.