hey just had a look on google and it seems that basically a healthy diet is the key, the most important nutrient you need is selenium because this is what converts the thyroid hormone.
here's what i saw for specific foods - 'A healthy diet for someone with hypothyroidism would include whole grains, natural foods, plenty of fruits and vegetables and a good supply of seafood and other lean protein. You should cut back on fatty meats. A multivitamin is probably a good idea if you don't already take one'
hope this helps