Studies examining whether transgender individuals are at increased risk for acute cardiovascular events associated with hormone therapy have been small, and the data have been inconsistent. To address this question, investigators evaluated electronic health records from three large U.S. health care systems, comparing the rates of venous thromboembolism (VTE), ischemic stroke, and myocardial infarction (MI) in 2,842 transfeminine (male-to-female) and 2,118 transmasculine (female-to-male) adults, with almost 100,000 cisgender men and women (those whose gender identity corresponds to their physiologic sex at birth), matched by age, study site, and race and ethnicity and followed for a mean of approximately four years.

In the transfeminine group, the incidence of VTE was higher than in the cisgender controls, with a risk difference of 4.1 and 16.7 cases per 1,000 person-years at two and eight years, respectively, relative to cisgender men, and 3.4 and 13.7 cases per 1,000 person-years at two and eight years, respectively, relative to cisgender women. The incidence of MI was higher in the transfeminine group than in the reference group of cisgender women but was not different from that in the cisgender men. The incidence of stroke was similar in the three groups. Among transfeminine individuals who started estrogen therapy during the follow-up period, however, incidence rates of both VTE and stroke were higher, with pronounced differences in risk, as compared with the cisgender men and women.

In the transmasculine group, the cumulative incidence of cardiovascular events was similar to that among the cisgender men and women, and the authors write that the evidence was not sufficient to draw any conclusions about the risk of events in the transmasculine group.

The study results provide evidence that estrogen therapy may be associated with an increased risk of VTE, and probably ischemic stroke as well, among transfeminine individuals. These results, the study authors write, also suggest a need for further and longer-term study and increased monitoring for cardiovascular events in transgender patients.-EM

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