I am increasingly convinced that the "thyroid hormones" T1, T2, T3, and T4 are simply a place to store iodine. When iodine is needed somewhere in the body it can be taken from T4, converting it to T3. But it's not the case that "T3 is the active form" as you'll read in the literature, it's that the removed iodine is the active or useful thing.<p>Changing the ratio of T3/T4 does cause a change in TSH (thyroid stimulating hormone) but that's IMHO simply a signal that the iodine is getting used, so please send us more.<p>There are other tissues in the body that need iodine, as evidenced by the sodium-iodine symporter present on those cells, so to set the recommended daily iodine intake based solely on what the thyroid can use is IMHO a huge mistake.<p>Some things with interesting iodine research: skin cancer, breast cancer, type 2 diabetes, asthma, polycystic ovaries, fibrocystic breast disease, other cancers. But yeah, it cures goiter...