In trans girls and transfeminine adolescents, finasteride is a medicine that may sometimes be prescribed for puberty suppression if there is a good reason why other antiandrogens, such as GnRH analogues and spironolactone, cannot be used.
Finasteride works by blocking the conversion of testosterone to its more potent form, dihydrotestosterone. Finasteride has widely been used as an antiandrogen in adult trans women and has been shown to be safe, well-tolerated, and effective in this population.
However, it is important to note that there is currently no research evidence on the use of finasteride in the adolescent population. For this reason, it is usually preferable to try a more established antiandrogen, such as spironolactone, before considering finasteride. Nonetheless, given the established safety and effectiveness of finasteride in the adult population, it is unlikely to be associated with any significant risks in the adolescent population.