Men with a type 2 5-alpha reductase deficiency, despite normal testosterone levels, did not experience male pattern hair loss.

“later on there were anecdotal pieces of evidence from this island in papua new guinea where these men over expressed with this genetic mutation called a type 2 5 alpha reductase deficiency and what it showed us is that it's not testosterone overall that's causing hair loss but rather these men with this very specific type 2 5-alpha reductase deficiency also never lost their hair to male pattern hair loss and yet had normal testosterone levels”