Yes it is and there is a rather simple explanation. The thyroid gland has limited capacity for storing iodine and iodine tablets make sure it's saturated with

Yes it is and there is a rather simple explanation. The thyroid gland has limited capacity for storing iodine and iodine tablets make sure it's saturated with the non-radioative isotope. Any more iodine (in this case radioactive) will then be excreted. This only works as 'radiation protection' when the saturation has been reached before being exposed to the radioactive iodine of course.