From wikipedia: "Men with androgenic alopecia typically have higher levels of 5-alpha-reductase, lower levels of total testosterone, higher levels of unbound/free testosterone, and higher levels of total free androgens including DHT."
Note that they say typically. Testosterone levels falling within a normal range really doesn't tell you very much when it comes to male pattern hairloss. As a indicator of whether you do have male pattern hairloss or not, the visible signs are much more important than blood tests.
Also remember that it's a combination of hormones and genetics that cause a man to start going bald, which means that blood hormone tests are completely missing a vital part of the picture.
To put it simply, DHT is the hormone implicated in male hairloss, and drugs such as Propecia (Finasteride) help with hairloss by stopping testosterone from converting into DHT.
Last edited by mattj; 09-16-2011 at 02:18 PM.