Measurements of triiodothyronine can serve as a prognostic indicator in acutely ill patients.
triiodothyronine-to-reverse triiodothryonine =
= (total triiodothyronine) / (reverse triiodothyronine)
where:
• Both total triiodothyronine and reverse triiodothyronine are in ng/dL.
Interpretation:
• 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
