http://chriskresser.com/
The short answer however is that the rT3 test is very expensive and the result does not change the treatment.
My understanding of the rT3 mechanism is that it is not biologically available but does interfere with the negative feedback loop. The body recognizes rT3 the same as it does T3 and does not produce more thyroid hormone. This is apparently why people with this problem have normal TSH and T4 levels. It was explained to me that in some cases the rT3 needs to be flushed out to allow for the active T3 to be made available. This is all dependent on the mechanism of the underlying issue of course.
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