Estrogen may increase risk of cardiovascular events in menopausal women

The results are published in the Journal of the American Heart Association.

Estrogen hormones play a key role in sexual development and reproduction in women. Estradiol is the most active hormone. Its blood levels are particularly high during the active reproductive period. After the menopause, the ovarian function ceases, leading to a significant drop in estrogen levels in the blood (the adipose tissue then becomes the main source of estrogen). However, low concentrations of these hormones do continue to circulate and may still exert biological actions.

Throughout their lives, women are less exposed to the risk of cardiovascular disease than men. For many years, this relative immunity displayed by women was attributed to estrogen undertaking a 'protector' role in terms of atherosclerosis and its complications. However, this hypothesis was not confirmed by recent research into the hormonal treatment of the menopause. estrogen administration does not prevent ischaemic arterial disease in menopausal women and could even have a harmful effect on women in the highest age bracket.

Until now, no study has been able to clearly identify the link between circulating endogenous sexual hormones and the cardiovascular risk in menopausal women.

Today, this knowledge gap has been reduced by the results of a French cohort study (Three City Study-3C) performed on approximately 6,000 women aged over 65 from among the general public. Estradiol levels in the blood were measured upon entry into the cohort and, after monitoring performed over a four year period, 150 new cases of cardiovascular disease had appeared.

For the first time, the results demonstrate that high estradiol levels in the blood lead to an increased risk of myocardial infarction or strokes, although the cause and effect link is not shown. This relation is not influenced by other known factors for cardiovascular risk, namely diabetes and obesity.

Other results show that estrogen seems to affect some mechanisms involved arterial obstruction, which causes cardiovascular disease. Although the coagulative effect of estrogen is clearly defined, significant research is now required to establish its role in the inflammatory process, particularly in obese women, where the accumulation of adipose tissues is associated with high estrogen levels.

This new data questions the beneficial role of estrogen on the heart and vessels. "Fresh studies must confirm this harmful effect and establish whether these results can be applied to younger menopausal women" stated Pierre-Yves Scarabin.