I have had these as well and although I was told that a lot of people with a thyroid condition do have dizziness, spinning, tinnitus and an off-balance sensation sometimes, I've always found mine goes with a treatment from either an osteopath, chiropractor or cranio-sacral therapist. It can all be caused by tight neck muscles (back and side of neck) or an unstable neck as well as by problems actually starting in the ear. I have injured my neck and back in the past and always put it down to that, but it's also noticeable to me that a lot of people with a thyroid problem who also have a muscular issue seem to find the muscle issues more persistent, or need more frequent osteopathic etc treatments than others with the same muscular issues but no thyroid problem. A lot of people also report that such things as back pain, neck pain, shoulder problems improve once they're on an optimal dose of thyroid hormones. If you push your jaw forward or back does the tinnitus alter at all? Do you have a thyroid problem and do you take thyroid hormones?
Edited to say that I've just seen your other post about thyroid and ectopic heartbeats and I'd agree with other there that you're not taking the right dose of thyroid hormones. Once you are, you may well find that the dizziness and tinnitus either stop or can be better controlled by physical therapists.