Thyroid issues are very common today.  A major reason for this is the widespread problem of iodine deficiency.  Up until the late 70's, iodine was used as a dough conditioner in commercially baked goods, but then the industry decided to replace the iodine with bromine, a hallide/toxin similar to fluoride and chlorine that takes up residence in the body where iodine should be.  I believe in direct correlation to this, we saw breast cancer rates skyrocket in the 80's, and I would say about 75% of all adults I work with for whatever reason have some form of a thyroid disorder.  Iodine, selenium, and glutathione are key to protecting and nourishing the thyroid gland and assisting the smooth functioning of thyroid hormone conversion.  Here are many resources from my files shedding light on thyroid health.  See Iodine & Selenium & Glutathione for more info.