Thyroxine, Total (TT4)

 

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

 

 4.5 - 12.5 µg/dL


CPT CODE

84436


INFORMATION

 

 The hormone thyroxine (T4) is the main product secreted by the thyroid gland and is an integral component of the hypothalamus-anterior pituitary-thyroid regulating system. It has the function of anabolically influencing metabolism. Thyroxine is formed in a coupling reaction from two DIT molecules (3,5-diiodotyrosine) in the thyroid gland. It is stored bound to thyroglobulin in the lumina of the thyroid follicles and is secreted as required under the influence of TSH.  The major part (>99%) of total thyroxine (T4) in serum is present in protein-bound form. As the concentrations of the transport proteins in serum subject to exogenous and endogenous effects, the status of the binding proteins must also be taken into account in the assessment of the hormone concentration in serum. If this is ignored, changes in the binding proteins (e.g. due to estrogen-containing preparations, during pregnancy or in the presence of a nephritic syndrome etc.) can lead to erroneous assessments of the thyroid metabolic state.

The determination of T4 can be utilized for the following indications: the detection of hyperthyroidism, the detection of primary and secondary hypothyroidism and monitoring of TSH-suppression therapy.

USC ENDOCRINE SERVICES LABORATORY
126 W. Del Mar Blvd 
Pasadena, CA 91105-2508
Phone: (855) 224-7111
Fax: (855) 224-7123

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.

1975 - 2020. All Rights Reserved.