Measurements of triiodothyronine can serve as a prognostic indicator in acutely ill patients.


triiodothyronine-to-reverse triiodothryonine =

= (total triiodothyronine) / (reverse triiodothyronine)



• Both total triiodothyronine and reverse triiodothyronine are in ng/dL.



• The ratio serves as an index of catabolism.

• Patients with poor outcome following tend to have reduced ratios, with decreases in triiodothyronine and increases in reverse triiodothryonine.


Free triiodothyronine:

(1) normal levels in children and adults are 4.0-7.4 pmol/L; this is 0.2-0.5% of total triiodothyronine

(2) normal ranges in pregnant women vary with trimester (3.2-5.9 in first trimester; 3.0-5.2 in second and third trimesters)

(3) acutely ill patients who do not survive have lower levels than patients who do

(4) levels < 1.0 pmol/L are associated with high risk of death


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