Diagnosed with Graves' disease 12 years ago. Had radioactive iodine treatment went underactive - 50 microgram levothyroxine, then 75 microgram. Treated for breast cancer 2010 and been on Arimidex for 5 years. Suddenly thyroid has become overactive again reduced dose levothyroxine to 50 and very recently 25 awaiting appointment with endo. Has anyone else had strange problems with levels?