• androgenetic alopecia;
  • dutasteride;
  • identical twins


Objectives  This study compared the efficacy of dutasteride vs. placebo in the treatment of male pattern hair loss (androgenetic alopecia) in 17 pairs of identical twin males with androgenetic alopecia over a 1-year period.

Methods  In this randomized, double-blind, placebo-controlled, single-center study, one twin from each identical twin pair received dutasteride 0.5 mg/day for 12 months while the other received placebo for 12 months. Hair growth was evaluated using standardized clinical photographs, hair counts, and patient self-assessment questionnaires.

Result  Dutasteride significantly improved hair growth at 1-year compared to placebo based on the analysis of the investigator assessment and the patient self-assessment questionnaires. Sixteen of 17 sets of twins completed the study, of which 15 sets correctly predicted the use of dutasteride. Only one set could not determine the active drug from the placebo.

Conclusion  Through the use of identical twins, this randomized trial provides evidence that dutasteride significantly reduces hair loss progression in men with male pattern hair loss.