Oestrogen and stroke in women: assessment of risk.

The Women's Health Initiative reported an increased risk of stroke with hormone therapy, which has had a major effect on the use of these drugs. The increased risk was unexpected because research with animals showed that oestrogen reduces the extent of experimental strokes, and in human beings, oestrogen improves endothelial-dependent blood flow and lipid profiles. The mechanisms of risk might be related to oestrogen's proinflammatory and prothrombotic effects. However, the overall risk is still uncertain because of the complex actions of oestrogen at different doses, with or without progesterone, and the presence or absence of atherosclerotic risk factors. A similar debate about oral contraceptives and stroke risk in young women continues as data accumulate. Further studies are needed to identify the mechanisms of risk of stroke with oestrogen, as well as the risk factors that put women at particularly high risk of stroke with these hormones.