Previously:
Disclaimer: I am not a medical professional and this is not medical advice.
Cyproterone acetate (CPA) is widely used as an antiandrogen for trans women and transfeminine people outside of the United States, lowering testosterone levels as part of feminizing HRT. In addition to blocking androgen receptors, CPA is also a strong synthetic progestin, acting on the progesterone receptor more powerfully than bioidentical progesterone itself (Hammerstein, 1990). Long-term use of CPA has been established as a risk for developing meningiomas, a type of usually benign brain tumor that expresses progesterone receptors and is stimulated to grow by strong progestins such as CPA (Korhonen et al., 2006). Many of these tumors would otherwise be small and asymptomatic; CPA may not produce them, but it can cause them to grow larger and become symptomatic, requiring treatment with surgery or radiation.
Meningioma has been found to occur more often in those assigned female, who as a group tend to experience higher progesterone levels over their lifetime than those assigned male (Wiemels, Wrensch, & Claus, 2010). Multiple studies of large cohorts of trans women taking CPA have found that they are more likely to develop meningiomas than the general population (Ter Wengel et al., 2016; Nota et al., 2018), and studies of cis women and cis men revealed that high doses of CPA were linked to a greater likelihood of meningioma (Gil et al., 2011). Weill et al. (2019), examining a cohort of 131,485 cis women in France, established that greater cumulative exposure to CPA over time was associated with a steadily increasing meningioma risk, and the European Medicines Agency subsequently stated that any dose of 10mg or more should only be used “once other treatment options, including treatment with lower doses, have failed”. Continue reading
