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 "Science News Science News Of The Week
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At the close of a woman’s childbearing years, her body undergoes hormonal changes that render her more vulnerable to a number of degenerative conditions, especially heart disease and osteoporosis. Drug therapy can slow or forestall that vulnerability.
However, the recipe of hormones most commonly prescribed in the United States may not fill the bill-at least in lowering heart risks, several new studies indicate. That’s troubling, maintains veterinarian Kent Hermsmeyer, who coauthored two of the studies, because heart disease kills three out of every four post-menopausal women. Hormone therapy delivers estrogen to make up the shortfall that occurs with menopause. To prevent the rise in breast cancer risk that typically develops when women receive estrogen alone, physicians often prescribe a combination that contains a second hormone usually a synthetic form of progesterone. The new studies suggest that this duo’s heart benefits depend on the form of progesterone used.
Hermsmeyer’s team at the Oregon Regional Primate Research Center in Beaverton gave estrogen daily to 18 rhe-sus monkeys whose ovaries had been removed to simulate menopause. Six also got natural progesterone, while another six monkeys received the syn-thetic medroxyprogesterone acetate (MPA), the most widely prescribed pro-gesterone for postmenopausal U.S. women. After 4 weeks, the researchers injected the animals with two chemicals released by blood platelets, simulating a heart attack. In monkeys receiving MPA and estrogen, this injection provoked an unrelenting constriction in the coronary artery, cutting off blood flow. Unless treated within minutes, the animals would have died, says Hermsmeyer. This chemical challenge produced the same result in animals that had received no hormone therapy.
Monkeys that had been treated with estrogen alone or together
with natural progesterone quickly recovered normal blood flow without
drug treatment. The researchers report their findings in the March NATURE
MEDICINE and the March 1 JOURNAL OF THE American COLLEGE OF CARD-OLOGY. “The big surprise,” Hermsmeyer says, is that “MPA poses
such a huge risk. This is a really dangerous drug.” J. Koudy Williams of Wake
Forest Uni-versity’s Bowman Gray School of Medicine in Winston-Salem, N.C.,
was less surprised by the findings. He says new data from his team’s experiments
on monkeys show that MPA can “obliterate the beneficial effect
of estrogen [therapy] on the progression of coronary artery atherosclerosis.” Peter Collins of the National Heart and Lung Institute
in London and his colleagues saw similar effects in 16 women with coronary artery
disease. Participants in their study received two hormone replacement therapies,
each for several weeks. The therapies contained estrogen plus
natural progesterone or MPA. The women exercised on a treadmill until tests showed
they were experiencing reduced blood flow to the heart. They could exercise
significantly longer when natural progesterone was part of the hormone therapy.
“There appeared to be a negation of the beneficial effects of estrogen
by MPA but not by natural estrogen’s benefits. -J. Raloff MARCH 8, 1997
Studies Announced at Annual AHA Meeting
NEW ORLEANS-At the American Heart Association’s (AHA) annual scientific meet-ing held Nov. 10, the results of two studies were announced, the first of which pertains to a high intake of fatty foods. Cardiologists at the University of Maryland Medical Centre in Baltimore found that after consuming high-fat meals, blond vessels do not dilate nor-mally. However, if people con-sume high doses of vitamins C and E before eating, it is more likely that the blood vessels will dilate properly. The researchers tested 20 healthy candidates who ate a 900-calorie meal of fast food eggs, hash browns and sausage, which contained 50 percent saturated fat. Average blood-vessel dilation before the meal was 21 per-cent, while average blood-ves-sel dilation after the meal was 12 percent. Average blood-ves-sel dilation two hours after consuming one gram of vita-minC, 800 IU of vitamin E and the fast-food meal was 17 percent.
The second study exam-ined the effect of soybean pro-tein, namely tofu, on menopause. Dr. Gregory L. Burke at the Bowman Gray School of Medicine in Winston-Salem, N.C. studied 43 women between the ages of 45 and 55 who experienced at least one strand of hot flashes or night sweating on a daily basis. These women were given 20 grams of powdered soy protein for a period of six weeks, and for the following six weeks, they were given powder carbohydrate.
Researchers indicate that soy protein may have a positive effect on menopausal symptoms such as hot flashes due to its key ingredient, phy-toestrogens, which are plant forms of the female hormone estrogen. Studies suggest that phytoestrogens have a similar effect on the human body as the female hormone estrogen, however, they are 1,000 times less potent. Researchers also believe soy protein to be a factor in alleviating the effects of menopause in women because symptoms such as hot flashes do not frequently occur in Asian countries where soy products are much more com-mon. According to Burke, phy-toestrogens are consumed at a rate of 50 milligrams per day in Japan, while in his study, the women were consuming 34 milligrams per day.
