Gender-Affirming Hormones Not Tied to Thrombosis With Short-Term Use

(Reuters Health) – Transgender adolescents and young adults on gender-affirming hormone therapy don’t appear to be at increased risk of thrombosis with short-term use, a new study suggests.

Researchers followed 611 transgender youth (median age 17 years) on gender-affirming hormone therapy for a median 554 days for estrogen users, and 577 days for testosterone users. The majority of youth were either overweight (24.2%) or obese (34.5%) based on BMI; and many (15.4%) were smokers or had other risk factors for thrombosis such as a family history (8%).

Seventeen participants were referred for hematology evaluation before initiating hormone therapy due to a personal or family history of thrombosis or a known risk factor for this condition. Three patients were recommended to initiate thromboprophylaxis prior to hormone therapy initiation.

None of the patients in the study developed venous thromboembolism or arterial thrombosis while on gender-affirming hormone therapy.

“There have been concerns about thrombosis risk with gender-affirming hormone therapy because some studies of transgender adults have shown an increased risk of thrombosis with use of hormones,” said senior study author Dr. Tanya Kowalczyk Mullins, an associate professor of pediatrics and director of research in the division of adolescent and transition medicine at Cincinnati Children’s Hospital Medical Center in Ohio.

“This study may not have found an increased risk of thrombosis due to the relatively short follow-up time,” Dr. Mullins said by email.

The study included 182 transgender women (29.8%) took estrogen for gender-affirming hormone therapy and of 429 transgender men (70.2%) who took testosterone. They all had levels of estradiol and testosterone monitored while they were taking hormones.

For estradiol users, the median estradiol level was 47.2 pg/mL and the median testosterone level was 189.5 ng/dL at the most recent measurement. For testosterone users, the median estradiol level was 33.2 pg/mL and the median testosterone level was 413ng/dL.

One limitation of the study is that researchers lacked data on use of estrogen-based contraception or menstrual suppression therapy, making it possible that some transgender men were still using estrogen when they started gender-affirming hormone therapy, the study team notes in Pediatrics.

Another drawback is that some participants may not have reached target physiological levels for hormones at the time that researchers measured hormone levels, and some may have still be in the processes of dose titration for gender-affirming hormone therapy.

Most study participants were also transgender males on testosterone therapy, and previous research suggests that testosterone is not associated with an increased risk of thrombosis, said Dr. Mick van Trotsenburg, a transgender healthcare specialist at University Hospital St.Poelten-Lilienfeld, in Austria, who wasn’t involved in the study.

Previous research suggests that the thromboembolism risk is associated with estrogen therapy, and less than one-third of the study participants were on this treatment, Dr. van Trotsenburg said by email. Venous thromboembolism is a serious adverse event associated with estrogen treatment in both cisgender and transgender patients, he said.

“VTE may result in a potentially lethal complication such as pulmonary embolism, and deserves, therefore, serious attention,” Dr. van Trotsenburg said. “However, VTE under estradiol at this age is rare.”

SOURCE: https://bit.ly/2OSwCPN Pediatrics, online March 19, 2021.

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