I take compounded timed release T3 for my thyroid. Due to the autoimmune disease, Graves, I had radioactive iodine treatment to kill off my thyroid. Something went wrong and it didn't kill my thyroid, but severely damaged it. I didn't find this out for years as thyroid tests said I was fine but I had severe hypothyroid symptoms. After special tests were done they found the problem and I have been on T3 for years and don't know what I do without it. Standard Synthroid (T4) does not work for me.