Testosterone converts to DHT with the aid of the enzyme Type II 5-alpha reductase, which is held in a hair follicle's oil glands (sebaceous). Scientists now believe that it's not the amount of circulating testosterone that's the problem but the level of DHT binding to receptors in scalp follicles. DHT shrinks hair follicles, making it impossible for healthy hair to survive.
The hormonal process of testosterone converting to DHT, which then harms hair follicles, happens in both men and women. Under normal conditions, women have a minute fraction of the level of testosterone that men have, but even a lower level can cause DHT- triggered hair loss in women. And certainly when those levels rise, DHT is even more of a problem. Those levels can rise and still be within what doctors consider "normal" on a blood test, even though they are high enough to cause a problem. The levels may not rise at all and still be a problem if you have the kind of body chemistry that is overly sensitive to even its regular levels of chemicals, including hormones.
Source: American Hair Loss Association
