Iodine
An essential element in the diet used by the thyroid gland to make thyroid hormones.
The two most important thyroid hormones are thyroxine (T4) and triiodothyronine (T3).
Thyroxine (T4) has four iodine molecules attached to its structure, while triiodothyronine (T3) has three iodine molecules attached to it.
Iodine is found in seafood, bread, salt, and seaweed.