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 The risk of a dangerous type of blood clot, called a venous
thromboembolism, nearly doubles for people transitioning from male
to female compared to both non-transgender men and women,
researchers reported in Annals of Internal Medicine.
The risk seems to come from hormone therapy. Among transgender women
who had started the therapy, the clot risk was five-fold higher
after two years of follow-up compared to non-transgender men and
three times higher compared to non-transgender women.
And although women have lower rates of heart disease than men, the
odds of stroke and heart attack for transgender women remain the
same as they would be if they had not transitioned.
For transgender men, the researchers could not confirm any health
risks because number of incidents was too small.
The study did not look at specific formulations, combinations or
doses of the hormones used in gender confirming therapy, so it
remains possible that some regimens pose a lower risk than others
and that's where future research should focus, senior author Michael
Goodman, a professor of epidemiology at the Rollins School of Public
Health at Emory University in Atlanta, told Reuters Health in a
telephone interview.
"These risks need to be weighed against the important benefits of
treatment," he said. "Our hope is people will understand we're not
trying to scare anybody. We're just saying there are some questions
that need to be answered to guide the therapy. Risks comes with
benefits, and benefits come with risks. It takes a thoughtful
healthcare provider and a well-educated patient to make an informed
decision."
"I don't think this would dissuade anyone" from transitioning
because the process is so important to those who feel they need it,
Dr. Alice Chang, an assistant professor in the division of
endocrinology, metabolism, diabetes and nutrition at the Mayo Clinic
in Rochester, Minnesota, told Reuters Health by phone.
Chang, who was not involved in the research, said most doctors
usually discuss such risks with patients, based on suggestions of an
elevated risk of heart disease and stroke seen in smaller studies of
people who have received hormone therapy for other reasons.
Until now, the data on whether gender confirming medical therapy
treatment poses cardiovascular risks has been sparse.
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The Goodman study used the cases of 2,842 transgender women and
2,118 transgender men. They were treated in California and Georgia
in the Kaiser Permanente health system. They typically had been
followed for about four years and only about 23 percent had
undergone gender confirmation surgery. The records of 48,686 men and
48,775 women who had not undergone gender confirming treatment, all
matched for race, ethnicity and year of birth, were used for
comparison.
Clot rates were twice as high for all transgender women. But in the
key subset that had begun estrogen therapy, the odds of developing a
potentially-dangerous clot were 5.1 times greater after two years
compared with non-transgender males.
When it came to the risk for developing a stroke caused by a blood
clot, the odds for transgender women were 9.9 times higher compared
to men in the control group and 4.1 times higher than for women in
the control group, based on a follow-up period of more than six
years.
Taking hormone therapy as a transgender woman did not increase the
odds of a heart attack compared to non-transgender men in the
control group. The risk was 2.4 times higher compared to female
controls, but women are less likely to have a heart attack in that
age group anyway.
It took about two years for the risks to become clear, and they
increased over time.
"There were so few events because the patients tended to be young,"
said Goodman.
Chang agreed with Goodman that the findings will shift the focus on
the safest way to give hormone treatments. A higher risk may not
have been seen in transgender males because they receive their
testosterone as an injection or a patch, she speculated.
"This is the first large study that says we need to be aware of this
(cardiovascular risk) and a lot of unanswered questions about
duration, type and dosing of therapy have to be answered," she said.
SOURCE: http://bit.ly/2MWDN2A Annals of Internal Medicine, online
July 9, 2018.
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