New research from Karolinska Institutet shows that long-term treatment with sex hormones in transgender people can lead to significant changes in body composition and risk factors for cardiovascular diseases, particularly in transgender men. The study is published in the Journal of Internal Medicine.
“We saw that transgender men treated with testosterone increased their muscle volume by an average of 21 percent over six years, but also that the amount of abdominal fat increased by 70 percent,” says Tommy Lundberg, a professor in the Department of Medicine at Karolinska Laboratory. Institute. “In addition, they had more liver fat and higher levels of ‘bad’ LDL cholesterol, which can increase the risk of cardiovascular disease.”
The researchers followed 17 adult transgender men and 16 transgender women who were prescribed treatment with testosterone and estrogen, respectively. They used magnetic resonance imaging (MRI) to map body composition and measured metabolic risk factors through blood tests, blood pressure and vascular stiffness. The scans were performed before the start of hormone therapy, after one year and after five to six years.
The results show that long-term hormone therapy leads to several important changes in both body composition and metabolic risk factors, particularly in transgender men. Changes in fat volumes continued over time, while the greatest changes in muscle mass and strength occurred after only one year of treatment.
“Previous studies in this area were conducted for a relatively short duration, up to two years,” explains Tommy Lundberg. “Our results show that it is important to continue monitoring the long-term effects of hormone therapy in transgender people to prevent cardiovascular disease and other health problems.”
In transgender women who received estrogen treatment, the changes were not as pronounced. Their muscle volume decreased by an average of seven percent after five years of treatment, while muscle strength remained unchanged. Transgender women increased their total fat volume but gained less abdominal fat.
As part of the study, muscle, fat and skin tissue samples were also taken. The next step is to analyze these tissue samples to understand the interaction between genetic sex and sex hormones. Researchers are investigating, among other things, how hormone treatment affects skeletal muscle gene expression and the mechanisms behind changes in adipose tissue.
“In addition to health aspects, our research contributes to increasing knowledge about reasonable expectations regarding the masculinizing and feminizing effects of sex hormone treatment,” says Tommy Lundberg. “However, some of the changes were relatively modest and should raise caution regarding expectations of large, long-term changes in this group of patients.”
The research was funded by the Stockholm Region, the Thuring Foundation, the 1.6 Million Club, the Karolinska Institutet Center for Innovative Medicine, the Swedish Research Council, the Swedish Medical Association, the Novo Nordisk Foundation and the European Foundation for Diabetes Studies.
Two of the co-authors are employees of AMRA Medical AB. Tommy Lundberg has received compensation for expert opinions on issues related to skeletal muscle changes in transgender people and reimbursement for traveling to speak on the same topic.