A new Snippet about the effects of reverse T3 on type-2 diodinase has been added. This is a complex subject. It appears that rT3 inhibits T4 to T3 conversion in the brain with no effects on thyroid blood tests (TSH, fT3, fT4) and no effects on markets such as heart rate. An additional consideration is that rT3 has a protective role in acute illnesses such as ischemic stroke which may have adverse consequences in patients taking high dose liothyronine or NDT.