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1 - 3 days
Turnaround time is defined as the usual number of days from the date of pickup of a specimen for testing to when the result is released to the ordering provider. In some cases, additional time should be allowed for additional confirmatory or additional reflex tests. Testing schedules may vary.
For more information, please view the literature below.
0.5 mL (Note: This volume does not allow for repeat testing.)
Red-top tube or gel-barrier tube
If a red-top tube is used, transfer separated serum to a plastic transport tube.
Distinguish between high T4 levels due to hyperthyroidism and due to increased binding by TBG in euthyroid individuals who have normal levels of free hormones; document cases of hereditary deficiency or increase of TBG; work-up of thyroid disease. In patients with low T4, high T3 (uptake) or the reverse, who clinically seem eumetabolic and have normal FTI, measurement of TBG is only occasionally needed. Some such patients may have hereditary anomalies of TBG. TBG is increased by estrogens, tamoxifen, pregnancy, perphenazine, and in some cases of liver disease, including hepatitis. Decreased TBG is found with some instances of chronic liver disease, nephrosis and systemic disease, and with large amounts of glucocorticoids, androgens/anabolic steroids, and acromegaly. Although alterations of TBG are usually resolved by the thyroid profile, TBG must occasionally be directly measured.
Kindreds are described with elevated TBG and hyperthyroxinemia as a harmless genetic abnormality. They have normal levels of TSH and free T4 and decreased T3 uptake.2 Structural variants of TBG are inherited as X-chromosome-linked traits, most inherited structural abnormalities in TBG cause decreased affinity for thyroid hormone.3
TBG is normal in familial dysalbuminemic hyperthyroxinemia, an entity which can be incorrectly identified as thyrotoxicosis.4 Triiodothyronine uptake was described as having produced information equivalent to TBG in a study of 372 subjects.5
Immunochemiluminometric assay (ICMA)
1 to 11 m
1 to 3 y
4 to 6 y
7 to 12 y
13 to 18 y
|Order Code||Order Code Name||Order Loinc||Result Code||Result Code Name||UofM||Result LOINC|
|001735||Thyroxine Binding Globulin||3021-3||001735||Thyroxine Binding Globulin||ug/mL||3021-3|
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