Triiodothyronine, Total (TT3)

 

METHODOLOGY

Electrochemiluminescence Immunoassay (ECLIA)

 

PERFORMED  

 

Tuesday & Friday

REPORTED  

2 days

COLLECT  

 

One 6mL RT (Min: 4mL RT)

TRANSPORT  

 

1 mL refrigerated serum (Min: 0.5 mL)


STABILITY  


Stored at 2 - 8°C until used; Stable if frozen at - 20°C 

UNACCEPTABLE SPECIMENS  

Do not use heat-inactivated samples.


REFERENCE RANGE

 

 80 – 180 ng/dL


CPT CODE

84480


INFORMATION

 

 Triiodothyronine (T3) is the hormone principally responsible for the effects thyroid hormone on the various target organs. T3 (3, 5, 3’– triiodothyronine) is mainly formed extra-thyroidally, particularly in the liver, by enzymatic 5’–deiodination of T4. Accordingly, the T3 concentration in serum is more a reflection of the functional state of the peripheral tissue than the secretory performance of the thyroid gland. A reduction in the conversion of T4 to T3 results in a fall in the Total T3 concentration. It occurs under the influence of medications such as propanolol, glucocorticoids or amiodarone and in severe non-thyroidal illness (NTI), and is referred to as the “low T3 syndrome”. As with T4, over 99% of T3 is bound to transport proteins, primarily TBG. However, the affinity of T3 to them is around 10-fold lower than for T4.  The determination of T3 is utilized in investigations of the etiology of hyperthyroidism.

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Email: endolab@usc.edu

The USC Endocrine Services Laboratory is licensed by the State of California, Department of Health Services, and accredited by the College of American Pathologists, and certified by Medicare according to the provisions of the U.S. Department of Health and Human Services Clinical Laboratory Improvement Act of 1988.

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