Although initial experimental data and results of observational studies suggest that hormone replacement therapy
(HRT) is associated with a reduction in the risk of heart disease, the results for events such as stroke or thromboembolism
are less clear. Randomized secondary and primary prevention studies have found that HRT is not protective
against the risk of coronary heart disease, stroke or progression of atherosclerosis. Therefore, HRT therapy should not be
initiated to prevent vascular disease among postmenopausal women. There are numerous explanations for the divergent
findings of observational and randomized clinical trials of HRT. For example, study design and differing biological effects
of HRT on vascular risk factors.
The use of HRT for young postmenopausal women with moderate to severe menopausal vasomotor symptoms appears to
be safe. The absolute risk of vascular event associated with HRT is low and varies depending on factors like age or years
since the menopause. The presence or absence of cardiovascular risk factors determines the differences in vascular risk
linked to HRT.
Further studies should identify the mechanisms involved and determine whether and how different regimens of HRT influence
vascular risk as well as the influence of individual patient characteristics.