Mahidol University trial: 3% minoxidil raised mustache density 17% in transgender men in 12 weeks

Researchers at Mahidol University in Bangkok, Thailand, report that topical 3 percent minoxidil increased facial hair density in transgender men, ScienceAlert reports. The work was a randomized, double-blind, placebo-controlled trial. The results were published in The Journal of Dermatological Treatment. sciencealert.comScienceAlertsciencealert.comOpen source ↗

Trial design and results

Thirty-four participants receiving gender-affirming hormone therapy applied 3 percent minoxidil to the face twice daily for 12 weeks. Another 35 participants used a placebo.

At 8 weeks, the minoxidil group had denser, thicker facial hair than the placebo group. At 12 weeks, mustache density was up by roughly 17 percent and beard density by 15 percent from baseline. Many participants also reported better quality of life and higher satisfaction scores.

Side effects such as itching, red skin and flakiness were minimal, and no serious adverse events were reported. Participants' blood pressure remained stable throughout. sciencealert.comScienceAlertsciencealert.comOpen source ↗ Minoxidil is a known blood vessel dilator, and if enough of the drug is absorbed it could in theory cause dizziness, low blood pressure or rapid heartbeat. The authors, led by dermatologist Kantarat Wattanawinitchai, wrote that the safety profile is reassuring given these theoretical concerns about systemic absorption.

Background and limits

Minoxidil was first developed in the 1970s as an oral drug for high blood pressure. In 1988 the US Food and Drug Administration (FDA) approved a topical version, marketed as Rogaine, for male-pattern hair loss. It was later approved for female pattern hair loss. A 2016 study in cisgender men was the first to show that topical 3 percent minoxidil improved beard growth compared with a placebo.

A separate case report describes identical twins, one of whom applied 5 percent minoxidil to the beard and mustache area for over a year. After 16 months he had a greater hair count and density in both areas than his brother, who did not use the drug.

The current trial included only transgender men, so it is unclear whether the results apply to other groups. Ongoing testosterone therapy might act synergistically with minoxidil. Research is at an early stage, and topical minoxidil is not approved by the FDA for facial hair in any group, although it is sometimes recommended off-label. The Thai team argues it should be considered a first-line adjunctive treatment for transgender men whose facial hair development stays incomplete despite adequate testosterone therapy. sciencealert.comScienceAlertsciencealert.comOpen source ↗ The American Academy of Dermatology advises consulting a dermatologist first and notes that raw, irritated skin is a common side effect.