CHICAGO — Cross-sex hormone treatment of transgender adults leads to very few long-term side effects, according to the authors of the largest study to date to examine this issue.
More than 2000 patients from 15 US and European centers participated in the retrospective study, called Comorbidity and Side Effects of Cross-Sex Hormone Treatment in Transsexual Subjects, and nearly 1600 received at least 1 year of follow-up, the authors reported.
"Our results are very reassuring," principal investigator Henk Asscheman, MD, PhD, who heads HAJAP, his clinical research company in Amsterdam, the Netherlands, told Medscape Medical News. "There are mostly minor side effects and no new [adverse events] observed in this large population."
The primary serious side effect, venous thromboembolism, occurred in 1% of persons undergoing male-to-female (MTF) transgender transition and was due to estrogen treatment.
Among the 1596 adults who completed follow-up, 1073 were MTF and 523 were female to male (FTM). The MTF group had a mean follow-up of 5.6 years and a mean age of 35.0 years, and on average, the FTM group had a follow-up of 4.5 years and age of 27.5 years.
More than 70% of the MTF group received cyproterone acetate (in Europe) or spironolactone, as an antiandrogen, in addition to estrogen treatment, he noted.
Among FTM subjects, more than 90% received intramuscular or topical (gel) testosterone administration.