"if the thyroid doesnt work you have to take the hormones. that has nothing to do with whether the rest of the body has Iodine or not."
But it does have something to do with it because if the rest of your body does not have sufficient iodine, your thyroid won't either. If your body does not have sufficient iodine, that puts you at risk for increased breast cancer.
What I'm trying to say is that perhaps it's not the fact that a person IS taking thyroid hormone that puts them at increased risk but the fact that they NEED to take thyroid hormone (because of Iodine deficiency).