Free Thyroxine In Serum

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Contents 1 Reference-interval 2 Clinical-significance 3 Increases 4 Decreases 5 Methods 6 Specimen 7 More General Terms 8 Additional Terms 9 References

Reference-interval

• 0.8-2.3 ng/dL (adult)
• 10.3-29.7 pmol/L

Clinical-significance

• free T4 is the active form of T4
• 0.02-0.04% of total plasma T4 exists unbound as free T4, the majority is bound to 1 of 3 plasma proteins, albumin, thyroxine-binding globulin, prealbumin compare with free T3 0.2-0.5%

Increases

• hyperthyroidism

Decreases

• hypothyroidism

Methods

• equilibirum dialysis immunoassay

Specimen

• serum, refrigerate immediately, stable for 7 days at room temp, but storage at 4 C preferred

More General Terms

• general chemistry test
• thyroid function test

Additional Terms

• thyroxine (T4)

References

Clinical Guide to Laboratory Tests, 3rd edition, NW Tietz ed, WB Saunders, Philadelphia, 1995

thyroxine [T4] (free) in serum