same here!! For me it was weird...I had been running like a mad woman for 6 months and had terrible shin splints...went to the doc for THAT and found out about the thyroid issue. It takes awhile to get the meds right, but once they were right, I felt much better and my runs did seem better. That was about a year and a half ago, and now I'm starting to feel that sluggish feeling again and I'm feeling something in my throat when I swallow again, so I'm wondering if the meds are off. Need to get it checked out...but rest assured you are not alone and it will get better once you get the dosage right.