Hormone therapy was linked to changes in heart electrical timing
In transgender adults, a heart electrical timing measure lengthened after feminizing hormone therapy and shortened after testosterone. The observational study did not establish changes in cardiovascular outcomes.
Based on the published abstract. The full paper may contain additional methods, results and limitations.
The 30-second takeaway
In transgender adults, starting feminizing hormone therapy was associated with a longer QTc, an interval measured on a heart electrical tracing; starting testosterone was associated with a shorter interval. These findings concern an electrical measurement. They do not show that either treatment caused more or fewer abnormal heart rhythms or other cardiovascular events.
This was an observational study from one center, with a smaller subgroup measured before and after treatment initiation. The abstract does not report cardiovascular event outcomes or individual follow-up lengths.
Changes after starting therapy
After therapy initiation, mean QTc change was 20 milliseconds (SD 12) in 15 transgender women and -17 milliseconds (SD 16) in 18 transgender men, compared with their pretreatment measurements. SD describes variation; assessment timing was not stated.
What the thresholds show
No participant had QTc above 480 milliseconds or a change above 60 milliseconds after starting therapy. These observations concern electrical measurements and cannot establish long-term cardiovascular safety or quantify abnormal-rhythm risk.
The original publication
Transgender-Affirming Hormone Therapies, QT Prolongation, and Cardiac Repolarization.
Grouthier V, Matamala M, Tabarin A et al.
JAMA Netw Open · 2025
- PubMed ID
- 40736733
- Record checked
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