FREE T3

Code
600.3539
Name
FREE T3
Category
None
Department
Chemistry
Start Date
Expiration Date
Synonyms
T3 Free, Triiodothyronine (Free), FT3
CPT Codes
84481
Site
Main Lab
Reference Test
ATLAS Test Code

Specimen Information

Type

Gold, SST

Volume

1.0 ml

Transport Info

Refrigerated
7 days stability

Frozen (Freeze Only once)
1 month stability

Fasting Required?
False
Patient Instructions

Reference Range

2.5-3.9 pg/mL

Methodology

Chemiluminescence

Clinical Significance

Measuring T3 is useful when altered concentrations of total T3 occur due to changes in T3 binding proteins, especially thyroxine-binding globulin (TBG).

Triiodothyronine is one of the thyroid hormones present in serum that regulates metabolism. Determination of this hormone concentration is important for the diagnostic differentiation of euthyroid, hyperthyroid and hypothyroid states. The major fraction of total triiodothyronine is bound to the transport proteins (TBG, prealbumin, albumin). Free triiodothyronine (fT3) is the physiologically active form of the thyroid hormone triiodothyronine (T3).The determination of free T3 has the advantage of being independent of changes in the concentrations of binding properties of the binding proteins; additional determination of a binding parameter (T-uptake, TBG) is therefore unnecessary.The sequential testing procedure and the use of a labeled antibody reduces the possibility of interference due to altered binding properties of the serum, as can occur with assays employing labeled antigen (analog method).

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