I've had an underactive thyroid for 20 years, before my UC diagnosis. Since my take down over 2 years ago it has been hard to get the medication under control. It appears to be at a stable range now. If it starts going all over the place again I'm going back to see an endocrinologist. There is more than the one test they usually give you so if you think you are having problems that are not being detected I'd suggest you see an endocrinologist.