Dutasteride works by blocking the enzyme 5α-Reductase, which converts testosterone to dihydrotestosterone (DHT).
DHT is the hormone that is responsible for causing hair loss.
This is because it causes hair follicles to shrink so hair grows thinner, is weaker, and falls out more quickly. Eventually, the hair is not strong enough to break the surface of the scalp, leading to complete baldness. As Dutasteride blocks the enzyme 5α-Reductase, less DHT is produced.
This allows hair to regrow from the follicles that were previously affected as a result of DHT, as well as preventing further hair loss.