Fluorine, Bromine, Chlorine are very similar molecularly to iodine. The thyroid needs iodine to function properly. So what happens is the iodine is displaced by the Fluoride, Bromide and Chlorine. Then your thyroid becomes full of the toxic minerals rather than iodine.

God only knows what this may cause-possibly hypothyroidism. The only way I know to rid the body of fluoride is with Iodine supplementation. If you are really toxic the detoxing symptoms from bromide and fluoride can be pretty wicked.

Here is a site that talks about iodine in more depth.
http://www.alkalizeforhealth.net/Liodine2.htm