A new study published in JAMA Network Open suggests that gender-affirming hormone therapy (GAHT) may subtly influence a common heart enzyme, causing levels to shift toward those typically seen in a person’s affirmed gender.
Researchers in Australia followed 152 healthy transgender adults, 78 beginning feminizing hormone therapy and 74 beginning masculinizing therapy, along with cisgender men and women for comparison. Blood samples were collected before treatment and again after 12 months to measure high-sensitivity cardiac troponin I (hs-cTnI), a protein released into the blood when the heart muscle is stressed or damaged.
Hs-cTnI is a key marker doctors use to detect heart attacks and assess cardiovascular risk. In cisgender populations, average levels differ between men and women. Men’s levels are generally higher, likely due to larger heart muscle mass. For transgender patients, however, there has long been a question of which reference range to use after starting hormone therapy.
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The Study’s Findings
After one year of hormone therapy, researchers found a measurable shift in hs-cTnI levels:
- Trans women (those assigned male at birth who began feminizing hormones) showed a decrease in hs-cTnI levels, aligning more closely with cisgender women.
- Trans men (those assigned female at birth who began masculinizing hormones) showed an increase in hs-cTnI levels, aligning more closely with cisgender men.
These results suggest that GAHT may cause heart enzyme levels to adjust in the direction of a person’s affirmed gender within the first year of treatment.
What This Means
Experts caution that these changes do not necessarily reflect better or worse heart health. Instead, they may simply show that hormone therapy can influence biological markers in ways consistent with hormonal shifts. The authors note that doctors should consider a patient’s affirmed gender and the duration of hormone use when interpreting heart enzyme results.
This is one of the first longitudinal studies to track these cardiac markers in transgender adults with matched cisgender comparison groups. While promising, the research comes with caveats. The sample size was modest, follow-up lasted only a year, and the study did not include imaging tests like echocardiograms to link enzyme changes with physical heart differences.
Why It Matters
For transgender people, accurate medical interpretation can be a matter of safety. Understanding how GAHT influences lab results could help prevent misdiagnosis or unnecessary alarm when test values shift. It also underscores the importance of inclusive, gender-affirming research that studies transgender participants directly rather than assuming one-size-fits-all medical norms.
The authors call for larger, longer studies to confirm these findings and to explore whether shifts in cardiac markers eventually affect heart function or risk. For now, the results are a useful reminder that our bodies adapt to who we truly are, and science is beginning to catch up.
