Cyproterone acetate is an antiandrogen that is often used in feminising hormone treatment to suppress testosterone. As well as blocking the testosterone receptor, cyproterone acetate suppresses the production of testosterone, which makes it a very effective antiandrogen.
While the majority of people who take cyproterone acetate tolerate it without complications, a recognised side effect of cyproterone acetate is liver impairment, which occurs in less than 10% of people who take cyproterone acetate. This can range from mild elevations of liver enzymes to acute severe liver failure. While rare, fatalities have been reported from liver failure induced by cyproterone acetate.
For this reason, cyproterone acetate is contraindicated in people with evidence of liver impairment. Also, people who are taking cyproterone acetate are required to have regular blood testing to check their liver markers.
Liver health can be assessed by a blood test for liver markers, also known as liver function tests. These measure enzymes that are produced by the liver and which are elevated in the blood when the liver is damaged. The most sensitive markers of liver injury are the enzymes alanine transaminase (ALT) and aspartate transaminase (AST). However, liver function tests can also include other markers, such as alkaline phosphatase (ALP), gamma-glutamyl transferase (GGT), bilirubin, and albumin.
If your ALT or AST levels are elevated beyond the healthy reference range, then it is possible that you have some degree of liver impairment, and so cyproterone acetate is not recommended for you. If you are taking cyproterone acetate and your ALT or AST levels are elevated, it is recommended that you stop taking cyproterone and instead consider a different antiandrogen.
It is also recommended that you see your doctor to investigate the liver injury further. Your doctor may wish to monitor your liver health with a repeat blood test or arrange further investigations, such as an ultrasound scan of the liver.
If you have had to stop cyproterone acetate because of liver injury, alternative antiandrogens are available which do not affect the liver. These include gonadotropin releasing hormone analogues (nafarelin, triptorelin, leuprorelin), 5-alpha reductase inhibitors (finasteride, dutasteride), and spironolactone.
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