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.

The main ones

• Spironolactone: the usual choice in the US. A blood pressure and fluid tablet that also blocks androgens.
• Cyproterone acetate: common in the UK, Europe, Australia and much of Asia. Not available in the US.
• GnRH agonists: injections or implants that switch off testosterone production at the source. Used by some UK gender services.
• Bicalutamide: blocks testosterone from acting rather than lowering it. Used by some prescribers, with less evidence behind it.

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.

Not always needed

Estrogen on its own lowers testosterone too, and some prescribers use estrogen without a separate blocker, called monotherapy. After an orchiectomy, the anti-androgen is usually no longer needed. Anti-androgens compares them in full.

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