Synonyms
Total Triiodothyronine
Clinical Significance
Total T3 may be used to help diagnose hyperthyroidism or a pituitary gland disorder, evaluate the cause of an overactive thyroid, and monitor a patient’s response to treatment of hyperthyroidism. The total T3 test measures both bound and free T3, while the free T3 test measures only the T3 that is not attached to protein.
Specimen
Serum
Stability
7 days at 4 to 8 °C
30 days at -20 °C
72 hours at ambient temperature
Reference Range
0.23 – 3.08 nmol/L
Interpretation
| TSH | FREE T4 | FREE OR TOTAL T3 | THYROID FUNCTION |
|---|---|---|---|
| Normal | Normal | Normal | Normal Thyroid Function |
| High | Normal | Normal | Subclinical Hypothyroidism |
| High | Low | Normal or Low | Primary Hypothyroidism related to the Thyroid gland |
| Low or Undetectable | Normal | Normal | Subclinical Hyperthyroidism |
| Low | High | High | Primary Hyperthyroidism related to the Thyroid gland |
| Low | Low | Low or Normal | Secondary Hypothyroidism related to the Pituitary gland |
| Normal or High | High | High | Secondary Hyperthyroidism related to the Pituitary gland |
Limitation
A number of factors can impact the T3 level in the blood, including: Pregnancy, Disease and Medications.