Dihydrotestosterone and dihydrotestosterone/ratio can be used to differentiate sexual differentiation diseases (DSD). In 5a-reductase deficiency, DHT levels may be abnormally low in comparison to testosterone levels. The ratio of testosterone to DHT should be measured, according to guidelines.
DHT levels may also be measured to assess the efficacy of 5a-reductase inhibitor therapy in female alopecia.