My cat has hyper-thyroid, she suffered through it (without me knowing what was going on) for about 6 months before she started to get real thin and always needing to eat. There was also some problems with her peeing around the house. She also had an enlarged heart, due to the thyroid pumping her full of natural speed.
Vet prescribed her with Tapazole (methimazole) and she's been fine ever since, all the abnormalities went away except for the enlarged thyroid. The pills were pretty expensive, but I found a place that sells a 15 month supply for ~$180 plus shipping & handling.
I know this doesn't help know, but I think that if its possible - you may wanna find a new vetinary clinic. Just IMO.
-SW