A Radioimmunoassay for Measurement of 3,3',5'-Triiodothyronine (reverse T3
 Nonstandard abbreviations: TFT, thyroid function test; TSH, thyroid-stimulating hormone; fT4, free thyroxine; fT3, free triiodothyronine; rT3, reverse T3
; HHE, hepatic hemangioendothelioma; D1, type 1 iodothyronine deiodinase; CNS, central nervous system; T2, diiodothyronine.
But what if the patient had a TSH of 2.4, again normal, but a low normal free T3 and free T4 with a high normal reverse T3
? Reverse T3
is a form of T3 that mimics T3 hormone but fails to function adequately as thyroid hormone.
Why would our bodies have the potential to make a destructive molecule like reverse T3? Let's go back 1000 years to what was Germany (my mother was 100% German).
Two last notes on this case: First I was taught (in some forgotten conference) that food intolerances can also activate D3 and increase reverse T3 and create the illusion of hypothyroidism with normal T4 and TSH values.
Leptin resistance causes a diminished TSH secretion, a suppressed T4 to T3 conversion, an increase in reverse T3, an increase in appetite, an increase in insulin resistance, and an inhibition of lipolysis.
Low intracellular leptin levels are inversely correlated with reverse T3, which may currently be the best marker, along with the T3/T4 ratio, for diminished T4 to T3 conversion and cellular hypothyroidism in chronic illness.
High reverse T3 levels in manic and unipolar depressed woman.
Opposite effects of dexamethasone on serum concentrations of 3, 3',5'-triiodothyronine (reverse T3) and 3,3,5"-triiodothyronine (T3).
Likewise, if the reverse T3 level is elevated, then it will further inhibit the conversion of T4 to T3.
A low ratio of T3 to reverse T3 is a predictor of mortality in congestive heart failure patients.
You've read before about the importance of the "rT3" (reverse T3
) lab test in evaluation of hypothyroidism.