Medical Study Concludes:

Estrogen Protects Arteries

Contributed by Elizabeth Parker and Jodie

NEW YORK (Reuters)

Researchers have found evidence that the hormone estrogen can protect blood vessels against coronary artery disease in men as well as in women.

The findings appear to confirm the belief that the lower rate of heart disease in women before menopause is due to their higher levels of the hormone.

In two separate studies, the arteries of male-to-female transsexuals taking high doses of estrogen for five years were found to have a greater ability to expand in response to changing conditions -- such as exercise -- and to medication than those of men not taking estrogen.

Moreover, transsexuals and premenopausal women showed a similar ability for their arteries to expand in response to stimuli.

The transsexuals had been using the hormone to help their bodies make the transition between genders.

"There aren't too many men who take a lot of estrogen," says the senior author of one study, Dr. David Celermajer of the Royal Prince Alfred Hospital in Sydney, Australia, "because estrogens have the well-known side effects of growing breasts, changing body shape, and causing facial hair loss -- all the things that we call 'feminizing' effects."

"But there is one group of genetic males in the community who do take high-dose estrogen, and that's male-to-female transsexuals," he says.

The Sydney study compared 15 genetic males who had been taking estrogen for an average of five years to 15 other males matched for age, vessel size, and heart disease risk factors such as smoking.

Using ultrasound imaging of the brachial artery in the right arm, the researchers looked at the artery's responses to the inflation and deflation of a blood pressure cuff.

They also looked at the artery's reactions after study participants took the heart drug nitroglycerin, which is used to widen blood vessels.

The smooth muscle cells in the arteries of the transsexuals were found to expand more readily after pressure cuff changes and to the medication. These findings suggest that estrogen helps improve the ability of arteries to meet the blood flow demands of the heart.

A similar pattern was observed in the other study, which was conducted by cardiology researchers at Monash Medical Centre in Melbourne, Australia.

In this study, 14 transsexuals taking estrogen for five years were compared with 14 age-matched men and 15 premenopausal women. Compared to the men, the brachial arteries of the transsexuals and women had a greater capacity to widen in response to the blood pressure cuff and to nitroglycerin.

The researchers also note that despite similar total cholesterol levels among the study participants, the transsexuals and the women had higher levels of heart-protective HDL cholesterol.

In addition to having a 23% higher level of HDL than men, the transsexuals also had 23% lower LDL cholesterol, high levels of which are known to be associated with an increased risk of heart disease.

"Clearly, more studies into the short- and long-term effects of estrogen in men are required, in particular, studies into the mechanisms by which estrogen may exert its effects," the Melbourne researchers state.

SOURCE: Journal of the American College of Cardiology

(1997;29:1432-1436, 1437-1444)


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