THYROXINE-BINDING GLOBULIN (TBG), SERUM

General Information

HLAB/HOL Code: TBG
UPHSM LIS Test #: 9060
Schedule:
Testing Time:
Testing Lab: Labcorp

Specimen Info
Only 1 specimen type required, unless otherwise specified

Volume: 0.5 (0.3) mL
Temperature: Refrigerate
Tube Type: Red-top tube or Yellow-top (Gel-Barrier) tube
Collection Info:
Specimen: Serum

Volume: 0.5 mL

Minimum Volume: 0.3 mL (Note: This volume does not allow for repeat testing.)

Container: Red-top tube or gel-barrier tube

Collection: If a red-top tube is used, transfer separated serum to a plastic transport tube.

Storage Instructions: Refrigerate

Specimen Acceptability

Serum

Methods

Immunochemiluminometric assay (ICMA)

Clinical Utilities

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.

CPT Codes

84442

* The CPT codes provided are based on AMA guidelines and are for informational purposes only. CPT coding
is the sole responsibility of the billing party. Please direct any questions regarding coding to the payer being billed.

Reference Range

Males: 13-39 ug/mL
Females: 13-39 ug/mL