Well, after ten days of being on thyroid meds, I finally had a possible side effect. Personally, I'm glad it wasn't one of the nasty ones, like seizures, but hives aren't exactly fun. Nothing disfiguring, mind you, and I was actually convinced that I just had a couple of bug bites. When I finally asked my wife if she'd been suffering from bug bites, and she said "no" I thought something might be up, and when the marks appeared across my back I was certain. My wife is pretty much mosquito bait on feet, so if she was fine, then I wasn't suffering from bug bites.
The doctor confirmed that I was having some kind of allergic reaction, but there's always a possibility that it's from something else (I've been snacking on peanuts A LOT this week) but the safest course is to stop the meds (and the nuts) until the reaction goes away. Once they clear up for a week I'll go back on the pills and see if they make a return.
Apparently, an allergic reaction is pretty rare in this situation, especially since I've exhibited no other side effects. I'm hoping that it's just that I overdosed on peanuts this week, but only because it will be easier to regulate what I eat than to adjust my thyroid.