I am to go tomorrow to get the radioactive iodine treatment for a hyperactive thyroid and was wondering if anyone could tell me what the normal amount of time is before I would become hypoactive. I am anxious to start replacement treatment of the hormone as the sooner I do the sooner I can get off prednisone which I detest as it is making me look like the pillsbury dough girl not to mention the fact that I now look at least four month pregnant!!