I went through a period of hyperthyroid about 4 years ago. It ruined my cross country season and made everything a challenge. I don't know how bad it is for you, but I dealt with extreme fatigue, muscle weakness, increased metabolism, and some other symptoms that don't stick out in my mind. For me it just took time, the last month of my season was fairly brutal and it was only after finishing my state meet about 80 seconds off where I was thinking I might finish that we really started to look for answers to what was wrong. It then just took a couple of months for my thyroid levels to normalize again and I haven't had a problem since. I'd just say hang in there, you can still run (I could at least) but it isn't easy or all that enjoyable at times. Hopefully you have something going on that will help you return to normal thyroid levels because like you said, it's tough.
I had hyperthyroidism once about 3 years ago. Developed it as a fluke occurrence after a bad cold. Made running for me pretty much impossible--terrible fatigue, dizziness, trouble breathing, etc. It took my doctor awhile to diagnoses b/c for one he didn't realize that I had an elevated heartbeat (a symptom of hyperthyroidism). I had a 70bpm when my normal resting rate was around 48-50bpm. Was advised to do nothing until my levels went back to normal. After that, I was better than ever.
PS The one "good" thimng about hyperthyropidism is the incredibly small amount of sleep you need...I was in school at the time-on a good night, I might sleep four hours.