Details
Back to Test DirectoryCPT Code
84439
Specimen Type
Blood
Container Type
Serum Separator Tube (SST)/Yellow
Stability
2-8°C, 6 days
Handling Instructions
Allow to clot for 30 mins, centrifuge within 2 hours
Clinical Notes
Total T4 consists of both bound and free fractions but only the free hormone is metabolically active. At any given time, most thyroxine is bound to thyroxine binding globulin (TBG), prealbumin, and albumin (>99.9%), with only a very small fraction (0.03% to 0.04%) free in the serum. Factors altering these carrier proteins will alter total T4 levels accordingly, but the free level (active fraction) is much less sensitive to changes in the serum binding proteins
Performing Lab
Principle Laboratory - Houston
16840 Buccaneer Ln
Suite 281
Houston, TX 77058
Principle Laboratory - Irving 6210 N Belt Line Rd #170 Irving, TX 75063