I just wondered if anyone had the same problem. I was diagnosed with an underactive thyroid (borderline) 8 years ago. My readings fluctuate greatly and one minute they put my dose up and then down again as it settles. However, every time they put it up I suffer months of racing heart beats and sleepless nights. I then ask to take a lower dose ie. 75mcg and it settles. I do wonder about whether I actually ever needed it. Do you think your body gets accustomed to having it therefore, begins to need it. I now have twitches and osteoporosis so these can be both to do with too much thyroxine. I now have to take propranolol but surely that must have an effect as that is for over active thyroid symptoms. I feel I am taking one pill to combat the other. There seems to be no referrals unlike other conditions. I look forward to hearing your comments.