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NAME | METHOD | REFERENCE RANGE | UNITS |
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Thyroxine (T4) Free | ICMA | < 3 days: Call Client Services
< 2 months: 0.9 - 2.2 < 19 years: 0.8 - 2 >= 19 years: 0.81 - 1.61 |
ng/dL |
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TYPE | VOLUME | TEMPERATURE | INSTRUCTIONS |
PRIMARY | ||||
1 | Serum | 1 (0.5) mL | Refrigerated - 4 Day(s), Frozen - 2 Month(s) |
Free thyroxine (Free T4) is used to evaluate thyroid function independent of binding protein status. T4 and T3 circulate in the blood as equilibrium mixtures of free and protein-bound hormones. Changes in concentration or affinity of TBG or other transport proteins profoundly affect the total hormone concentration in serum. The free hormone is independent of these binding protein variations and remains almost constant. |