Wow, interesting thread -- I was diagnosed with Chronic Inflammatory Demylenating Polyneuropathy (a mouthful) about seven years ago and put on Prednisone. Was diagnosed with Ulcerative Colitis last year and was put on Asacol. Still on Asacol, only take Prednisone when the CIDP flares up. My hair was thinning pre-medication, so I didn't notice any difference. And the couple of times I've let my hair grow back in, it doesn't seem any thinner than I remember it being.
Prednisone is a bear. Big weight gain, mood swings, etc. It does wonders, but the side effects are horrible.