Hormone therapy administration in postmenopausal women and risk of stroke.

HRT, consisting of estrogens alone, or in combination with a progestogen, is widely used for the relief of symptoms in postmenopausal women. Early observational studies have suggested that HRT might be associated with a reduced risk of cardio- and cerebro-vascular events. These encouraging results prompted randomized controlled trials assessing the risks and benefits of HRT in primary and secondary prevention of arterial vascular events. However, these clinical trials and further observational studies did not confirm the protective effect of HRT; it is now established that HRT increases the risk of stroke. This increased risk is mainly related to an increased risk of ischemic stroke. Oral estrogen alone and combined with progestogen are associated with a similar increased risk, which may be dose dependent. Conversely, a low dose of transdermal estrogens with or without a progestogen does not seem to be associated with such an increased risk of stroke, whereas the impact of tibolone, a synthetic steroid, remains uncertain. In summary, there is now a large amount of evidence demonstrating that HRT is associated with increased risk of stroke, in particular, ischemic subtype.