Starting a thread on this to try and get some info flowing on it. This is what i know about RT3. t4 hormones are sort of a precursor to t3 which is the active thyroid hormone, now under stress of any king be it psychological, infectious etc etc the body produces RT3 which basically inactivates the active t3 and down grades our metabolism. Now some gurus say this is a protective mechanism of the body where others say that this slowing down of the metabolism if chronic maybe stuck in this position and fixing this can help us to function alot more efficiently. For many all thyroid tests can comeback normal but rt3 isnt tested by alot of docs but it can be tested, also constant low body temp can be a sign as well. People on thyroid replacement which contains t4 can also have a high rt3 level. Its also mentioned that adrenal fatigue can also be caused by high rt3 but i have also read that low adrenals need to be treated before looking into thyroid treatments, but this point is controversial. But i cant see a reason not to try to slowly increase dhea etc before looking into this, some have treated adrenals and this has improved rt3 as well. Now some other things i have read on rt3 treatment involve treatment with t3 hormone only starting with a low dose and slowly increasing this to a tolerable level. those on t4 switch over to t3 only and later on to a mix of both t3/4 thyroid. Many only need to be on t3 treatment for a few months. Now i think how this works is that it supresses our own t4 production which rt3 comes from thus stopping rt3 and t3 therapy sort of burns off the rt3 that has built up. now when this is sorted and t3 therapy is stopped our body can produce t3 again from t4 without the high level of rt3 inactivating our t3 thyroid. Our body temp should come up to a more normal level 36.5-37c, sorry i dont know american temps. I have no personal experience with this or know much about dosing. hopefully those who have tried this and know more about this can share your experiences. Maybe this could indirectly help improve immune function?? cheers!!!