The safety and efficacy of finasteride for transgender men with androgenetic alopecia: a case series.

No serious adverse events occurred in any of the three transgender men treated with finasteride over 3 months.

• Three transgender men aged 44, 43, and 29 years participated in the clinical trial.
• All participants were of Asian ethnicity.
• Primary endpoints included the incidence of treatment-related adverse events at 1 week, 1 month, and 3 months.
• None of the patients experienced serious adverse events (above grade 2) at 3 months.
• All three patients continued treatment and extended to a total of 6 months.

All three transgender men showed improvement of at least one stage on the Norwood-Hamilton scale after finasteride treatment.

• Participants had been diagnosed with stage ≥ II androgenetic alopecia on the Norwood-Hamilton scale at enrollment.
• Improvements of at least one stage on the N-H scale were observed in all participants.
• Treatment began at 0.2 mg finasteride per day for 3 months (phase 1), then increased to 1.0 mg per day for an additional 3 months (phase 2).
• The dose escalation occurred only if no adverse events above grade 2 occurred during phase 1.

Two of the three participants experienced resumption of menstruation during finasteride treatment.

• Two out of three participants experienced resumption of menstruation, suggesting finasteride may reduce some effects of testosterone replacement therapy.
• All participants were undergoing testosterone replacement therapy and had not undergone hysterectomy.
• This finding indicates that finasteride's potential for reducing some of the effects of testosterone replacement therapy warrants further investigation.
• Participants were eligible only if they had not undergone hysterectomy, making menstrual resumption a detectable outcome.

The clinical trial enrolled transgender men meeting specific inclusion criteria related to age, surgical history, and alopecia severity.

• Eligible participants were transgender men (assigned female at birth, identifying as male) aged 20–60 years.
• Participants were required to be undergoing testosterone replacement therapy and to not have undergone hysterectomy.
• Androgenetic alopecia of stage ≥ II on the Norwood-Hamilton scale was required for enrollment.
• The trial was conducted from October 2021 to December 2023 and registered as jRCTs061210040.

Finasteride is approved in Japan exclusively for cisgender men and is not indicated for transgender men, providing the regulatory context for this trial.

• In Japan, finasteride's approved indication does not include transgender men.
• Testosterone replacement therapy is commonly used in transgender men for masculinization, and androgenetic alopecia is one of its most common adverse effects.
• This clinical trial was designed to evaluate safety and efficacy of finasteride specifically in transgender men.
• The primary endpoints were the incidence of treatment-related adverse events and the rate of participants continuing treatment at 3 months.