There is a NORMAL reaction, about one week (give or take) after RAI, when the thyroid cells damaged by the radioactive iodine release their stores of thyroid hormone into the blood. Not all cells are damaged at the same time necessarily, so we all have differing rates of response to this phenomenon. A week was the peak for me, it is different for others. So it is very normal to feel worse right after the RAI than you ever have before. It is simply an increase in your hyperactivity, and it goes away fairly quickly. (The half-life of thyroid hormone is approximately seven days for T4 and three-quarters of ONE day for the T3. So you can expect to have diminishing symptoms from here on out.)
One other thing you must keep in mind, too, is that the treatment is a process. It isn’t a quick fix. First it takes time for the thyroid cells to die out. Then it takes time to get our thyroid hormone levels to the place where they are supposed to be. We just have to hang in and know that we WILL get healthy again.
I hope this helps. I’m sure it was a nasty surprize to feel more rotten than ever. Your doctor should have explained it to you. I hope you are feeling better soon.
Bobbi