Feminizing Hormone Replacement Therapy (HRT) is a combination of medications that encourage fat redistribution (the way fat shifts in the face and other areas of the body can make a huge difference in appearance, and hormones are largely responsible for where and how we carry fat), breast growth, and reduce male pattern hair growth.
HRT isn’t for every transgender person, and every HRT patient has their own goals of therapy. So it’s worthwhile to know what medications are out there and what they do.
Spironolactone – Potassium-sparing diuretic, typically prescribed for high blood pressure, but lucky for us it also happens to block androgen receptors, meaning that androgens (testosterone and dihydrotestosterone) have less receptors available to bind to and activate.
Finasteride and Dutasteride – blocks the 5-alpha reductase conversion of testosterone to the more potent dihydrotestosterone (DHT). Finasteride selectively inhibits the type 2 isoenzyme, while Dutasteride inhibits both type 1 and 2 isoenzymes, which explains why Dutasteride results in lower DHT serum levels (by 90%) than Finasteride (by 70%)1. However, these medications do not inhibit the production or action of testosterone itself.
Oral/Sublingual/Transdermal Estradiol – 17-beta estradiol, a “bioidentical” estrogen (it’s chemically identical to what our bodies naturally produce). This comes in pill form that can be swallowed or dissolved under the tongue, and in transdermal patches.
Estradiol Valerate and Estradiol Cypionate (Depo-Estradiol) – 17-beta estradiol in the form of injections. Valerate gives higher peak levels of estradiol and estrone, but Depo’s duration of elevated estrogen levels lasts up to 11 days while Valerate’s duration lasts 7-8 days2.
Unfortunately, we have yet to have proper studies on progesterone’s effects on transgender HRT. Anecdotal reports include increased breast fullness, improved mood, and increased libido. Scientifically, progesterone does lower LH and testosterone levels in AMAB (Assigned Male at Birth) patients, and competes with T for 5-alpha reductase enzymes (blocking the conversion of T to DHT).
There is some evidence that progesterone as part of HRT may increase risk of cardiovascular disease and breast cancer. However, it should be noted that such studies were conducted on post-menopausal cis women taking medroxyprogesterone and conjugated equine estrogens to see if the inclusion of progesterone in post-menopausal HRT could aid in prevention of chronic diseases. Trans women are a different population taking the drug for different reasons so we really need our own studies in order to make a valid judgement.
1Nickel J. C. (2004). Comparison of clinical trials with finasteride and dutasteride. Reviews in urology, 6 Suppl 9(Suppl 9), S31–S39.
2Oriowo MA, Landgren BM, Stenström B, Diczfalusy E (April 1980). “A comparison of the pharmacokinetic properties of three estradiol esters”. Contraception. 21 (4): 415–24
3Grecu EO, Weinshelbaum A, Simmons R. Effective therapy of glucocorticoid-induced osteoporosis with medroxyprogesterone acetate. Calcif Tissue Int. 1990;46(5):294–299