New Studies Disparage Fears About Transgender Hormone Therapy

Mila Madison

The new research has been published in the AACC’s January Men's Health Issue of the Clinical Chemistry journal. The American Association for Clinical Chemistry (AACC), is a global scientific and medical professional organization dedicated to clinical laboratory science and its application to healthcare.

In the first study, a team of researchers led by Dina N. Greene, PhD, of the University of Washington in Seattle has found evidence of better outcomes related to blood clots in transgender women taking estrogen compared to premenopausal cisgender women taking oral contraceptives. Though the outcome showed a slightly higher rate of blood clots in transgender women taking estrogen (2.3 per 1,000 person-years) compared to the incidence rate of blood clots in the general population (1.0-1.8 per 1,000 person-years), it is less than the estimated rate in premenopausal women taking oral contraceptives (3.5 per 1,000 person-years). The results of the study show that transgender women who take estrogen are at a much lower risk for blood clots compared to cisgender women taking birth control pills.

Greene's team performed a systematic review of all studies that have included the incidence rate of blood clots in transgender women receiving estrogen therapy while identifying 12 that were the most relevant. Using meta-analysis, the researchers combined the results of these 12 studies and calculated a risk estimate that is based on all available evidence to date. 

In a second published study, a team of researchers led by Guy G.R. T'Sjoen, MD, PhD, conducted a systematic review of all studies measuring risk factors for cardiovascular disease in transgender people who are taking hormone therapy. The team identified 77 relevant studies, finding the majority of them show no increase in cardiovascular disease in either transgender men or women after being on hormone therapy for a period of over 10 years.

The study did reveal a higher cardiovascular disease risk for transgender women who had been taking ethinyl estradiol compared to other forms; however ethinyl estradiol is now considered obsolete and is no longer used.

Both research teams have indicated that though the research does much to overcome many misconceptions related to hormone replacement therapy, the sample sizes are small and they would like to see further research performed on a larger scale.

Currently, many transgender patients often experience difficulty finding adequate care when it comes to obtaining hormone replacement therapy. In many cases, even when care is found, many doctors do not have a sound understanding of what the long term effects of hormone replacement therapy would have on transgender patients and often provide inaccurate information regarding the risks. Due to the limited and conflicting information available, many doctors are denying patients treatment due to a lack of understanding regarding the risks. Currently, 1 in 4 transgender women are forced to obtain their hormones through illegal means.

"Documenting the risks associated with hormone treatment may allow for prescribers to feel more comfortable with prescribing practices, allowing for better overall management of transgender people," said Greene. "Our data support the risk of thrombotic events in transgender women taking estrogen therapy being roughly comparable to the risk of thrombotic risks associated with oral contraceptives in premenopausal women. Given the widespread use of oral contraception, this level of risk appears to be broadly accepted."