I was fine on T3 only until I got up to 56.5mcg. I then became EXTREMELY paranoid, anxious and insomniac. I also had a racing and pounding heart. Things were so bad that I had to go off it and re-start over on NTH. I was also low on iron and low iron can cause hyper like symptoms. I WILL be going on it again as I also suspect T3 resistance, but I will be supping iron and probably not going above 70mcg.