This review of current studies suggests that transgender hormone therapy is relatively safe for most people. The harms that do exist are relatively rare and can often be avoided with monitoring. The current literature is quite thin and larger, more carefully done studies are needed to address concern for more subtle harms.
Use of hormone therapy in transgender adults is safe when carefully monitored for certain risks, according to a study in the February 24 issue of the Journal of Clinical and Translational Endocrinology. The findings may help reduce concerns about hormone therapy among transgender individuals.
Researchers examined all studies on this topic that were published between 1967 and 2014. Overall, the findings were reassuring with no increased risk for cancer or death found. Hormone therapy was linked to an increased risk of blood clots in transgender women, increased blood count in transgender men, and changes in blood sugar levels in both transgender men and women. Other than these risks, there was little evidence of other serious health concerns from the hormones.
Estrogen Therapy May Increase the Risk for Blood Clots
Estrogen therapy may increase the risk for blood clots, which are clumps of hardened blood in blood vessels that may cause a heart attack, stroke, or other serious condition. In the largest and most recent trial to date, 1% of 1,076 transgender women taking estrogen therapy developed blood clots. Many studies in the past showed a higher risk for blood clots, but these studies included people taking a form of estrogen called ethinyl oestradiol that is no longer used. Other studies have linked the increased risk of blood clots to smoking, lack of movement after surgery, and having a disorder associated with blood clots. Treatment of high cholesterol and high blood pressure as well as not smoking may lower the risk for blood clots among transgender adults taking estrogen.
Transgender women on hormone therapy also may have an increased risk of stroke, cerebrovascular disease (a disease of the blood vessels in the brain), and heart attack.
Increased Blood Sugar and Cholesterol Levels Found
Increases in insulin resistance (meaning that the body does not use insulin properly) and blood sugar levels, as well as changes in body fat redistribution (where fat is stored in the body) were found in both transgender men and women. Slight increases in blood count (specifically, the number of red blood cells) were seen in transgender men.
In addition, hormone therapy in transgender women may lead to decreased sexual desire, but may lead to increased sexual desire in transgender men.
More studies on this topic are needed as most of the published studies include a small number of people or were case studies, meaning a study based on 1 person.
Weinand JD, Safer JD. Hormone therapy in transgender adults is safe with provider supervision; A review of hormone therapy sequelae for transgender individuals. J Clin Translational Endocrinol. 2015;2(2):55-60.