DHT (dihydrotestosterone) is a powerful "spinoff" hormone of testosterone. Therefore, as testosterone is produced DHT is likely to rise. Here's the problem - DHT essentially "attacks" hair follicles. Over time, DHT "stressed" hair follicles can no longer maintain normal hair production. This is a primary culprit of male pattern baldness, otherwise known as the dreaded "chrome dome."
If that weren't bad enough, testosterone support can result in higher levels of Estrogen.