Clinical Significance
T4 (Thyroxine), Total - For diagnosis of hypothyroidism and hyperthyroidism.
Preferred Specimen(s)
1 mL serum
Alternative Specimen(s)
Plasma collected in: Sodium heparin (green-top) or lithium heparin (green-top) tube
Minimum Volume
0.5 mL
Transport Container
Serum Separator Tube (SST®)
Transport Temperature
Room temperature
Specimen Stability
Room temperature: 7 days
Refrigerated: 7 days
Frozen: 28 days
Methodology
Immunoassay (IA)
Reference Range(s)
T4 (Thyroxine), Total
Male (mcg/dL) Female (mcg/dL)
<1 Month 4.5-17.2 4.5-17.2
1-23 Months 5.9-13.9 5.9-13.9
2-12 Years 5.7-11.6 5.7-11.6
13-20 Years 5.1-10.3 5.3-11.7
>20 Years 4.9-10.5 5.1-11.9
Free T4 Index (T7) 1.4-3.8