WINSTON-SALEM, N.C. – Research in monkeys suggests that the type of progestin in hormone therapy could dramatically affect heart attack severity. The study, by a Wake Forest University Baptist Medical Center researcher and colleagues, was reported today at the annual meeting of the North American Menopause Society in Washington, D.C.
"One type of hormone therapy limited heart muscle damage to only 5 percent while another resulted in permanent damage to 35 percent of muscle," said J. Koudy Williams, Ph.D., lead investigator, from Wake Forest Baptist. "If we can learn more about this mechanism we might be able to identify better hormone therapies for postmenopausal women."
For years, hormone therapy was prescribed as a way to prevent heart vessel disease in women. But then several research studies, including the Women's Health Initiative, showed that combination therapy (estrogen plus progestin) increased the risk of both a first and second heart attack in older women.
"These studies didn't look at the amount of heart damage that occurs if a postmenopausal woman has a heart attack," said Williams. "This is important to know because even though the drugs are no longer recommended to prevent heart disease, many women take them for menopausal symptoms or to protect their bones."
In a study of postmenopausal monkeys, Williams and colleagues compared the protestin in Prempro®, the most widely prescribed hormone therapy, with the progestin in Femhrt®. One group of monkeys got estrogen and the Femhrt progestin, one got estrogen and the Prempro progestin and one group didn't get hormone therapy. The monkey took the drugs for one year in doses equivalent to those prescribed to women.
The researchers then measured the amount of irreversible muscle damage that resulted after an experimentally produced heart attack. The Femhrt group had 5 percent muscle damage, the group that didn't take hormone therapy had 20 percent damage, and the Prempro group had 35 percent damage.
"We were very surprised," said Williams. "The two progestins produced dramatically different results."
The amount of heart muscle damage can affect risk of a future heart attack and risk of developing heart failure, the inability of the heart to meet the body's demands.
Williams said the results suggest that all hormone therapy drugs are not the same and that there may be better treatments than current formulations. He said, however, that the results are too preliminary to apply to women.
Next, the researchers want to learn how estrogen alone – without a progestin – will affect the amount of muscle damage. They also want to learn more about what caused the differences in muscle damage. They suspect that it is related to the amount of inflammation that occurs after a heart attack. They measured an enzyme that is a marker of whether white blood cells, which fight infection, are interacting with heart muscle cells. The Femhrt group had the lowest levels of the enzyme.
"We want to learn more about the inflammation pathway," said Williams. "By learning what treatments cause inflammation, we hope we can identify treatments to reduce it." The group, for example, wants to see how soy, which has anti-inflammatory properties, would affect muscle damage.
Progestin is a synthetic progesterone hormone. Progesterone is a female sex hormone essential for the healthy functioning of the reproductive system. In hormone therapy, progestin is used in combination with estrogen to reduce the risk of cancer of the uterus that occurs when estrogen is taken alone.
The progestin in Femhrt is norethindrone acetate. The progestin in Prempro is medroxyprogesterone acetate. Both groups of monkeys taking estrogen got the same type – ethinyl estradiol.
Other researchers were Irma Suparto, M.D., from the Institute Pertanian Bogor in Indonesia and Jacob Vinten-Johansen, Ph.D., a professor or surgery at Emory University.
Source: Eurekalert & othersLast reviewed: By John M. Grohol, Psy.D. on 21 Feb 2009
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