Study links HRT type with heart attack damage
10
October 2004
The type of hormone replacement therapy women take
could dramatically alter the muscle damage caused
by heart attack, US research on monkeys suggests.
Researchers, who presented their findings to the
North American Menopause Society in Washington
this weekend, found that one type of synthetic
progestin hormone limited heart damage to 5 per
cent, while another type resulted in damage to 35
per cent of muscle. Animals not given any hormones
suffered 20 per cent damage.
Previous studies, including the Women's Health
Initiative findings in 2002, showed estrogen plus
progestin therapy increased heart attack risk in
older women. But this was the first study to look
at the extent of heart attack damage, said lead
investigator Koudy Williams, of Wake Forest
University Baptist Medical Centre.
"We were very surprised," Dr Williams said.
"The two progestins produced dramatically
different results."
The findings followed news of a link between HRT
and increased risk of blood clotting called venous
thrombosis, particularly in obese older women.
In the new study, one group of postmenopausal
monkeys was given estrogen plus
medroxyprogesterone progestin (MPA), contained in
the most widely prescribed hormone therapy in the
US. The second group was given estrogen and
norethindrone progestin, contained in a competing
product. A third group didn't receive any hormone
therapy. Muscle damage was measured after inducing
heart attack.
The norethindrone group had 5 per cent damage and
the MPA group had 35 per cent damage.
Heart muscle damage could influence future heart
attack and heart failure risk, researchers said.
Both types of progestin are used in products sold
in Australia but were combined in the study with a
type of estrogen called ethinyl estradiol that was
not available here, said Susan Davis of the Jean
Hailes Foundation, an Australian women's health
research body.
Professor Davis was concerned that the study
described subject groups using product names, the
exact formulations of which were not used in the
experiments. Transferring animal results to humans
was also problematic, she said.
"What happens in animals is interesting but it
doesn't mean that anyone taking (MPA) should panic
and stop their HRT in case they get a heart
attack."
Dr Williams conceded that the research findings
were too preliminary to apply to women.
The researchers will conduct further studies into
the effects of estrogen alone on muscle damage and
the anti-inflammatory properties of soy.
"By learning what treatments cause inflammation,
we hope we can identify treatments to reduce it,"
Dr Williams said
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