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, and in parts of Asia it can be bought from a pharmacy without a prescription, which means nobody is checking the dose.

How it works

It acts in two ways. It blocks testosterone at the cell, and, because it is also a progestogen (a medicine that acts like progesterone), it tells the brain to cut the signal that makes the testes produce testosterone. The combination makes it very effective at lowering testosterone, often at doses much smaller than were once used. Doses used for trans women a decade or two ago are now generally seen as far higher than needed.

Not the same as Dianette

Cyproterone also appears in some combined pills for acne and contraception (Dianette and similar, sometimes called co-cyprindiol), paired with ethinylestradiol. That estrogen carries a clearly higher clot risk and is not recommended for feminizing HRT, so these pills are not a substitute for a prescribed regimen, whatever the forums say. Estrogen explains why.

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, with the risk rising with dose and years of use. European regulators restricted its use in 2020 because of it and advised the lowest effective dose. It can also lower mood, cause tiredness, raise prolactin and, rarely, affect the liver.

So monitoring on cyproterone usually includes prolactin and liver tests alongside testosterone and estradiol. Blood tests and monitoring covers the schedule, and risks and side effects covers each risk properly.

Common questions

The dose you started on is still right. Guidance has moved. If you have been on it for years, especially at an older, higher dose, it is fair to ask whether your regimen still reflects current advice.

Meningioma means you should stop today. The risk is tied to dose and duration, and stopping abruptly lets testosterone come back. Any change is a conversation with your prescriber, not something to do on your own.

You need it forever. Many people come off it after an orchiectomy or a vaginoplasty that removes the testes, because there is little testosterone left to suppress. Some switch to another anti-androgen or to estrogen alone (monotherapy) if their levels allow.

Symptoms worth reporting

Low mood that does not lift, persistent headaches, changes in vision, or nipple discharge are worth raising with your prescriber rather than putting up with; they can point to raised prolactin or, rarely, something that needs a scan. Yellowing of the skin or eyes or dark urine need a doctor the same day.

What to ask

Is my dose the lowest that does the job? How long do you expect me to take it, and what would make you switch? How often will prolactin and liver function be checked? If I am planning an orchiectomy, what happens to the cyproterone afterwards? Anti-androgens compares it with the alternatives.

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