How It Works
Anti-androgens (also called “androgen blockers” or “testosterone blockers”) are medications that block the effects of androgens, which is a family of hormones that includes testosterone. Anti-androgens can be added to estrogen to minimize the effects of androgens and to help achieve your desired level of feminization. Anti-androgens can also be used in anyone whose body produces testosterone to prevent effects that may be undesirable, such as hair thinning/balding on the scalp, heavy acne, or excess body/facial hair.
What to Expect
Some of the common effects of anti-androgens are slow. Typically, people would start to experience effects 1-3 months after starting. If you want to maintain the effects of anti-androgens, then they must be taking consistently. If you miss a lot of doses, or don’t take them as prescribed, then effects of androgens will increase which can lead to irreversible changes, such as irreversible hair loss/balding on your scalp. Anti-androgens may decrease in sex drive and functioning, including less erections or difficulty in maintaining them.
Types of Anti-Androgens
FINASTERIDE (“Proscar” or “Propecia”)/ DUTASTERIDE
How It Works: Finasteride is a daily pill that specifically prevents testosterone from becoming activated, which prevents it from acting on certain body tissues, including hair and skin. Therefore, it prevents hair thinning/balding and may also contribute to softer skin and slower regrowth of facial and body hair. Testosterone levels are not usually suppressed while on finasteride, but the effects are being blocked.
Risks: While finasteride has been studies extensively and is FDA-approved for preventing balding in cis males, it has not been studied much in transgender and gender diverse populations. Most of the time, finasteride has little to no side effects. Rarely, it causes decreased sex drive and function, numbing of mood, dizziness when standing, and breast tenderness and irregularity (lumps/bumps).
SPIRONOLACTONE (“Aldactone”)
How It Works: Spironolactone is a pill taken once or twice a day that blocks all androgen receptors, including testosterone. Since there are many androgens, blocking all of them can lead to side effects. Testosterone levels are usually suppressed on spironolactone.
Risks: Androgens regulate the salts and fluids in your body. Therefore, this medication leads to increased thirst, urination (possibly urination at night), low blood pressure, and high levels of potassium which can affect your heart and may need to be monitored with blood work. This medication is started gradually. Some people on spironolactone also report cloudy thinking and inattention. It also can interact with certain blood pressure medications and pain relievers (NSAIDs). If you have any kidney problems, please make your provide aware.
OTHER OPTIONS
While this sheet includes the most common medication options for blocking androgens, specifically testosterone, newer options are continually being developed and researched. For example, some research suggests progesterone decreases production of testosterone. Also, sometimes the “hormone blocker” medicine used to pause puberty in young transgender and gender diverse patients is used to block testosterone production if the more common methods do not work. Surgical interventions can also be used to permanently eliminate testosterone production. These other options typically have specific situations in which they used and significant risks that need to be considered. If you have questions about these options, please ask your provider for more information.
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