The only person who can tell you what level of exercise you may do at this point in time is your doctor.
There are a variety of reasons why exercise while hyperthyroid is problematic, if not downright dangerous. First, the dangerous part — while we are hyperthyroid our hearts are stressed. If you ever did aerobic exercises you may remember how we checked for our heart rate during the course of the program, to make sure that we were exercising at the proper level, the target heart rate, and not too high. It involved taking the pulse for ten seconds and multiplying by six (to get beats per minute). Anyway, while I was hyperthyroid a slow walk out to my mailbox on the street put my heart rate in the target zone. So, slow walking (not even boogying) was doing the job that exercise had previously done while I was hyperthyroid — at least as far as my heart was concerned. In addition, however, and worse, too high a level of thyroid hormone has been shown to cause heart arrythmias — i.e. excess thyroid interferes with the proper beat rhythm of the heart. Exercise can increase that danger. So, only your doctor can tell you when it is safe for you to exercise.
Once your doctor has given you permission to exercise again, you must start very slowly. Baby steps. We lose actual muscle while hyperthyroid. And trying to go back to previous levels of exercise too quickily can result in strains, pulls and tears, not to speak of shin splints.
Try to keep in mind that this, too shall pass. We do get well again. And we get well the quickest by working at whatever level is appropriate at the time. My "exercise" until I got my thyroid levels under control was rocking in a rocking chair (it utilizes muscles) and doing gentle, thorough stretching exercises on the floor. That was a bit of quasi-yoga. I had lost too much strength to do yoga poses, but I could do the breathing and some gentle stretches, and it DID relieve stress.
Wishing you good health again and soon.
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