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Women
who get hormone replacement therapy (HRT) through a skin patch
have higher levels of estrogen during exercise than women
who take HRT orally, but in most instances it probably is
not cause for concern, according to researchers at the University
of Virginia Health System.
"We
were wondering whether increased absorption of estrogen from
the patch during exercise could be high enough and prolonged
enough to reach a threshold for concern for increasing the
risk of adverse effects of excessive doses of estrogen such
as breast cancer," said Dr. Christopher Williams, assistant
professor of obstetrics and gynecology.
Researchers
followed 11 postmenopausal women on standard diets who were
given either estrogen pills or estrogen skin patches to use
for one month. After that month, the women exercised for 45
minutes during office visits. At 15-minute intervals during
their exercise, each woman gave blood samples that were tested
for growth hormone, cortisol, insulin, lactate, glucose and
estradiol and estrone, two potent estrogens. After four weeks,
the women switched to the alternate form of HRT and repeated
the treatment, exercise and blood sampling.
Researchers
found that estradiol levels changed significantly during exercise
for the women using the estrogen patch. However, the elevated
hormone levels returned to normal 30 minutes after exercising.
The other hormones did not change significantly during exercise
with either delivery method.
"Although
estrogen levels increased with exercise in the transdermal
estrogen patch users compared to the oral estrogen users,
the levels stayed elevated for only a short period of time
following exercise," said Williams. "It seems unlikely
that there are any increased risks due to elevated levels
of estrogen in active patch users. Perhaps an exception might
be women who use transdermal estrogen patches and have frequent
and prolonged exercise, such as marathon runners or long distance
bikers."
Source:
Medical Week staff,
week of June 16, 2002
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