Anti-Androgen

An anti-androgen is a medicine that lowers the effect of testosterone and other [androgens](/glossary/androgen), either by cutting how much the body makes or by stopping it from acting on the body's cells. In feminizing hormone therapy it is usually taken alongside estrogen.

Where you'll meet it

On nearly every feminizing prescription outside the few that use estrogen alone, and in almost any forum thread comparing plans between countries, because which anti-androgen you are offered depends heavily on where you live. In the Bangkok hospitals I work with, you can often guess a patient's home country from the anti-androgen on their medication list.

The main ones

• Spironolactone: the usual choice in the US. A blood pressure and fluid tablet that also blocks androgens. Cheap; potassium is checked.
• Cyproterone acetate: common in the UK, Europe, Australia and much of Asia. Not available in the US. Strong; now used at lower doses because of a link with meningioma.
• GnRH agonists: injections or implants that switch off testosterone production at the source. Used by many UK gender services. Effective, expensive.
• Bicalutamide: blocks testosterone from acting rather than lowering it. Used by some prescribers, with less evidence behind it and liver checks needed.

Anti-androgens compares them properly, side effects included.

Two ways of working

Some anti-androgens lower the amount of testosterone in the blood; others leave the level where it is and block its effect. That difference matters when a blood result comes back. On a blocker such as bicalutamide, a testosterone level that looks high does not mean the medicine is failing. Ask your prescriber which kind you are on and what the blood test is expected to show.

How it's judged

For the medicines that lower testosterone, the check is the testosterone level on your routine bloods. Guidelines commonly cite a target under about 50 ng/dL (under about 1.7 nmol/L), roughly the typical female range. Prescribers read it alongside estradiol, because estrogen is doing some of the suppressing too, and alongside how you are actually changing. Each medicine also brings its own extra tests: potassium and kidney function on spironolactone, prolactin and liver tests on cyproterone, liver tests on bicalutamide. Blood tests and monitoring sets out the schedule.

Common questions

An anti-androgen feminizes. It does not, on its own. It takes testosterone out of the way; estrogen does the building. Taking an anti-androgen without enough estrogen leaves you low on every sex hormone, which brings fatigue, low mood and, over time, bone loss.

Stronger is better. Pushing testosterone far below the target range adds side effects without adding feminization. The aim is enough suppression, not the lowest number on the sheet.

Everyone needs one. Estrogen on its own lowers testosterone too, and some prescribers use estrogen without a separate blocker, called monotherapy. It is more often reached with injections than with tablets.

After surgery, and on non-binary plans

After an orchiectomy or a vaginoplasty that removes the testes, there is little testosterone left to suppress, and most people stop the anti-androgen under their prescriber's guidance. Hormones and surgery covers what changes.

Some non-binary people want less androgen effect without full feminization, and ask about an anti-androgen with little or no estrogen. That leaves the bone question above unanswered, which is why prescribers are cautious. Non-binary routes goes through the options.

What to ask

Which anti-androgen, and why this one rather than the alternatives available where you live? Does it lower testosterone or block it, and what should your blood test show? What side effects should make you call, and what extra tests come with it? Is estrogen alone an option for you now or later?

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