It's possible the iodine is doing a good job of thyroid support, but your thyroid isn't up to the task of responding. So, it compensates for its inefficiency by growing larger. You may not be able to decrease the goiter till your TSH is lowered. That is what happened for me. Depending on how hypothyroid you are, a desiccated thyroid product such as Nutri-Mins might work, or you might need prescription-strength thyroid hormone replacement.