I had RAI 13 years ago. Been euthyroid on 150mcg thyroxine. All of a sudden seemingly screamingly 'hyper' again. Dose dropped to 125 then 100 mcg - felt dreadful, constipated, cold, fuzzy headed. Tried alternate day dosing, now back up to 125mcg and 'still over medicated' (TSH 0.01). Under consultant care. No explanation as to why suddenly 'hyper' again. (Says it is not my thyroid restarting...). Do we need less thyroxine as we get older/peri menopausal (now aged 45)?