I had my thyroid removed (cancer) 25 years ago and was on .125 mg Synthroid through young adulthood, 2 pregnancies and beyond. 2 years ago my primary physician said I should lower my dose, because new research showed a link w/ heart disease and too high dose and switched me to 100 Synthroad. Despite working out every day, I gained 35 pounds in the 18 months after the dose change. I kept being told my "range" was "normal." Well, it was normal on my old dose too!! I've recently moved and my new MD switched me back to my old dose. I am ever so slowly able to lose some weight (about 7 lbs in 3 months), but am starting to have trouble getting a good breath on many occasions. I actually feel better when I exercise. The little attacks are when I am sitting in the car or at work and they are very anxiety provoking. Any impliications here for my new-old dose? I went from a size 8 to a size 12 when my dose was changed down and could not stop the gain no matter what I did, but I didn't have these "anxiety" symptoms. Any advice?? Thanks so much.