3228 Thyroxine, (T4) Free

Components
NAME METHOD REFERENCE RANGE UNITS
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 


Specimen Requirements
TYPE VOLUME TEMPERATURE INSTRUCTIONS
PRIMARY
1 Serum 1 (0.5) mL   Refrigerated - 4 Day(s), Frozen - 2 Month(s)  


Clinical utility
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.


Reported: Same day

CPT Code: 84439

Notes: Also known as Free T4 (FT4).