Cyproterone Acetate

Cyproterone acetate is a tablet that lowers testosterone and blocks its effects. It is the most common [anti-androgen](/glossary/anti-androgen) for feminizing hormones in the UK, Europe, Australia and much of Asia, and it is not available in the US. Brand names include Androcur.

Where you'll meet it

On feminizing prescriptions outside the US, and in comparisons with spironolactone, which is its American counterpart. In the Bangkok hospitals I work with it is the one most patients arriving from Asia and Europe are already taking.

How it works

It acts in two ways: it blocks testosterone at the cell, and, because it is also a progestogen, it tells the brain to cut testosterone production. It is very effective at lowering testosterone, often at doses much smaller than were once used.

What gets watched

Cyproterone carries risks that have changed how it is prescribed. Long-term use at higher doses is linked to meningioma, a usually benign tumour of the brain's lining, and European regulators restricted its use in 2020 because of it. It can also affect mood, raise prolactin and, rarely, affect the liver. The trend has been towards the lowest dose that does the job, and to stopping it once it is no longer needed, for example after an orchiectomy.

If you are on it, low mood, headaches or changes in vision are worth mentioning to your prescriber rather than putting up with. Risks and side effects covers the rest.

← Back to the Glossary