From the Guidelines
Cyproterone acetate is a crucial anti-androgen medication in transgender feminine hormone therapy, used to block testosterone effects and achieve feminization when combined with estrogen therapy, such as estradiol. According to the most recent study 1, cyproterone acetate is among the most popular adjunctive androgen-lowering/-inhibiting agents, enabling lower doses of estrogen to be used. The typical regimen for transgender women includes estrogen and an adjunct antiandrogen to bring testosterone levels to <50 ng/dL, which is the female range.
Key Points about Cyproterone Acetate
- It works by preventing testosterone from binding to androgen receptors and reducing testosterone production.
- Typical dosing ranges from 12.5 to 50 mg daily, with many providers favoring lower doses (12.5-25 mg) to minimize potential side effects while effectively suppressing testosterone.
- Side effects may include fatigue, depression, liver enzyme elevations, and rarely, meningiomas with long-term high-dose use.
- Regular monitoring of liver function, prolactin levels, and mental health is recommended, as noted in the context of feminizing hormone therapy 1.
Considerations in Transgender Care
- Cyproterone is widely available in Europe, Canada, and many other countries but is not FDA-approved in the United States, where spironolactone is more commonly used as an anti-androgen.
- Cyproterone is generally considered more potent than spironolactone at suppressing testosterone, making it a popular choice in transgender care outside the US.
- The choice of anti-androgen and estrogen dosing should be individualized, considering the patient's response to therapy and potential side effects, as the optimal oestradiol doses or concentrations required to induce feminization are unclear 1.
From the Research
Cyproterone in Transgender Care
- Cyproterone acetate (CPA) is a competitive inhibitor of the androgen receptor and is often used in combination with estrogens in trans women to achieve feminization 2, 3, 4.
- The use of CPA in transgender care is aimed at suppressing testosterone levels, with studies showing that it is effective in achieving this goal 2, 3, 4, 5.
- However, CPA has been associated with side effects such as changes in liver enzyme concentrations and increases in prolactin concentrations 2, 3, 4.
Comparison with Other Anti-Androgens
- Studies have compared the efficacy of CPA with other anti-androgens, such as spironolactone, in lowering testosterone concentrations in trans women 3, 6, 5.
- One study found that CPA had a higher testosterone suppression efficacy than spironolactone 3.
- Another study found that spironolactone was an effective and well-tolerated alternative to CPA in patients with hyperandrogenism 6.
Dosage and Efficacy
- The optimal dose of CPA for transgender women has not been established, with studies suggesting that lower doses (10-20 mg/day) may be as effective as higher doses (50-100 mg/day) 2, 4.
- A study found that a daily dose of 10 mg CPA was equally effective in lowering testosterone concentrations in trans women as higher doses, while showing fewer side effects 2.
- Another study suggested that low-dose CPA treatment (10-20 mg/day) was as effective as high-dose treatment (50-100 mg/day) and possibly safer 4.