T4, FREE

Code
600.3500
Name
T4, FREE
Category
None
Department
Chemistry
Start Date
Expiration Date
Synonyms
FT4; Thyroxine, Free
CPT Codes
84439
Site
Main Lab
Reference Test
ATLAS Test Code

Specimen Information

Type

Gold, SST

Volume

1.5 ml

Transport Info

Refrigerated

Fasting Required?
False
Patient Instructions

Reference Range

0.4 - 5.9 ng/dL

Methodology

Fluorescence Polarization Immunoassay (FPIA)

Clinical Significance

The determination of free thyroxine is an important element in clinical routine diagnostics. Free T4 is measured together with TSH when thyroid function disorders are suspected. The determination of FT4 is also suitable for monitoring thyrosupressive therapy.

The thyroid hormone thyroxine (T4) is physiologically part of the regulating system of the thyroid gland and has an effect on general metabolism. The major fraction of the total thyroxine is bound to transport proteins (TBG, prealbumin and albumin). The free thyroxine (FT4) is the physiologically active thyroxine component.The determination of free T4 has the advantage of being independent of changes in the concentrations and binding properties of the binding proteins; additional determination of a binding parameter (T-uptake, TBG) is therefore unnecessary.

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