which gland can't produce its hormones unless it has enough iodine?
Three iodine molecules are added to make T3 (triiodothyronine), and four for T4 (thyroxine) -- the two key hormones produced by the thyroid gland -- so iodine is essential to the production of these two hormones of the master gland of metabolism. One needs the proper amount of iodine for optimal thyroid function. A severe iodine deficiency can cause hypothyroidism, and even developmental brain disorders and severe goiter. Less severe iodine deficiency is linked to hypothyroidism, thyroid enlargement (goiter) and hyperthyroidism. At the other end of the spectrum, excessive iodine intake -- both severe and moderate -- is also associated with hypothyroidism and goiter.