No, I'm not a vet. I'm a guy who has lived most of his life with cats and who has watched too many die sooner than they should simply because there was something that I didn't know. The information and opinions here are not intended to replace working with a vet, and if you have a hyperthyroid cat (or think you might), I strongly suggest that you join one of the groups listed below. I will sometimes disagree with your vet, but I cannot guarantee that anything here will work for you. What I ask is that you do some real thinking. I'll give references and reasons, but those aren't enough. Check what I say. The vet has a degree, but that isn't enough, either. Check what the vet says. Cats are quirky, something you've probably noticed, and that can make diagnosing and treating them a combination of science, empathy, experimentation, and luck.
The two groups listed below are almost certainly the largest accumulations of experience on the subject of feline hyperthyroidism and related problems. Some of the members have been working in the groups for many years, gathering information from many sources in addition to the results seen in the groups themselves. In addition, the people in the groups are largely those who will understand what you're going through, not the type to say, "just a cat". Even if things are going well on your hyperT adventure, I really suggest joining one of the groups. For what it's worth, I spend more time on the Facebook group but try to stay involved with both.Facebook Hyperthyroid Cats Group Yahoo Feline Hyperthyroid Group
We currently have quite a few fur-kin that we care for or help care for. All were strays at one time, and some have extra issues with one asthmatic, one FIV positive, one FeLV positive, and one hyperthyroid. The information and stories are free to all, and that especially applies to the medical material since I don't want to be accused of practicing without a license, but donations are certainly appreciated.