Preferred Specimen(s) 1 mL serum
Transport Container Plastic screw-cap vial
Transport Temperature
- Ambient 7 days,
- Refrigerated 7 days
Methodology Chemiluminescence
Clinical Significance Thyroxine (T4) is the major secretory hormone of the thyroid. Only 0.03% of T4 is unbound and free for exchange with tissues. Thyroid function may be assessed with thyroid stimulating hormone (TSH) and free T4 measured.