... in some portion of the population, it will cause Graves disease. And as everyone who has Graves knows, this is a very serious illness that will take quite a toll on your body, not something you can just shrug off, no matter how it goes or even whether you eventually heal from it.
I know this because my ingestion of iodine, in my attempt to normalize my sluggish thyroid, gave me Graves disease. This is a well-documented effect that has been demonstrated in iodine-poor communities that suddenly received supplementation in the food -- about 3-5% of the populace rapidly develop hyperthyroidism as a result. That low percentage means that you may very well be able to take Iodine without developing this lasting and difficult disease, but some others will not.