ESPE Abstracts

Background: The QT interval, corrected for sex and heart rate (QTc), measures the duration of the cardiac action potential and can indicate the risk of arrhythmias. The QT interval is typically longer in women compared to men; a phenomenon often attributed to estrogen's effects. However, conflicting data exist regarding the effects of gonadotropin-releasing hormone agonist (GnRHa) and gender-affirming hormonal treatment (GAHT) on QT intervals and dispersion. This study aims to investigate changes in QTc intervals among transgender/gender diverse (TGD) adolescents undergoing GnRHa and GAHT.

Methods: This prospective study included 39 TGD adolescents (20 TGD females), with a mean age of 15.6±1.4 years, all in Tanner stage 4-5. Participants were recruited between May 2017 -April 2020 at the Israeli Children and Adolescents Gender Clinic. Manual QTc interval measurements were taken from 12-lead ECGs. A board-certified pediatric cardiologist, blinded to the treatment, assessed the ECGs, defining long QTc as >450 ms and short QTc as <360 ms using the Hodges formula.

Results: QTc increased compared to baseline in 10 TGD females who initiated GnRHa alone and subsequently added estrogen treatment (381.9±17.7 ms at baseline vs. 403.1±21.2 ms on GnRHa alone vs. 403.1±21.1 on GnRHa and estrogen, P = .021). One participant, who was prescribed two psychiatric medications known to increase the QT interval, had a borderline increased QTc following estrogen treatment. In the 20 TGD females treated with a combination of GnRHa and estrogen, QTc increased compared to baseline (376.4±17.3 ms vs. 391.8±21.0 ms, P = .015). Among six TGD males, QTc decreased after the introduction of testosterone compared to GnRHa alone (383.2±13.3 ms at baseline vs. 402.0±23.3 ms on GnRHa alone vs. 377.0±18.0 ms on GnRHa and testosterone, P = .016). No significant change in QTc was observed in the 19 individuals treated with a combination of GnRHa and testosterone. Two individuals prescribed psychiatric medications exhibited a borderline/short QTc after adding testosterone. No arrhythmias were observed.

Conclusion: Treatment with GnRHa in both TGD female and male adolescents leads to the prolongation of the QTc interval, which persists after estrogen introduction but diminishes following testosterone treatment. Testosterone treatment in TGD males may induce a short QT interval in some individuals. These findings underscore the importance of monitoring QTc intervals in TGD adolescents undergoing hormonal treatments, particularly regarding potential interactions with psychiatric medications. Further research is warranted to assess QTc dynamics in this population.