New research finds an unexpected shift in heart biomarker to the affirmed gender, challenging long-held assumptions.
Gender-affirming hormone therapy (GAHT) likely alters both heart conduction and the heart muscle itself, say researchers from the University of Melbourne.
A year-long study of more than 150 adults has given the first prospective evidence of the impact of GAHT on high-sensitivity troponin I.
The troponin threshold to predict cardiovascular events is lower for women due to the greater cardiac mass typically seen in men.
Since estradiol and testosterone were not thought to directly impact cardiac mass, researchers expected that troponin would remain similar to individuals’ assigned gender at birth.
However, they found the opposite to be true.
The clinical research team found that troponin levels shifted towards the affirmed gender after 12 months of hormone therapy.
Troponin decreased in transgender women to a level not statistically different from cisgender women, but which was 78% lower than in cisgender men.
In transgender men, troponin increased to the range of cisgender men and became roughly seven times higher than in cisgender women.
Australian guidelines recommend sex-specific troponin thresholds, but confusion exists around how to apply them to transgender people taking receiving GAHT.
Affirmed gender reference ranges may be more appropriate for interpreting troponin tests in transgender people, lead investigator Professor Ada Cheung told media.
“This is important for reducing confusion in emergency settings and ensuring trans people receive safe, accurate care,” she said.
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Individuals initiating standard-dose GAHT were recruited between 2017 and 2022 and were tested at baseline and 12 months. Median participant age was 26 years.
The theory that sex hormones do not affect heart size or function after puberty has been increasingly challenged in recent years.
ECG studies have found that transgender women have smaller ventricular diameters than cisgender men, and higher testosterone has been associated with greater left ventricular mass.
The University of Melbourne team also found that GAHT changes QT intervals.
Researchers said the study represents an important step toward improving evidence-based, gender-affirming healthcare.
These discoveries have important implications for emergency medicine, the interpretation of ECGs and the use of cardiac biomarkers, they wrote.
