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TBG (Thyroxine Binding Globulin) (TBG)
Test CodeLAB128
Quest Code
870
Alias/See Also
TBG
CPT Codes
84442
Preferred Specimen
1 mL serum in gold top tube
Minimum Volume
0.5 mL
Other Acceptable Specimens
Plain red top tube
Transport Container
Transport tube
Transport Temperature
Room temperature
Specimen Stability
Room temperature: 7 days
Refrigerated: 7 days
Frozen: 28 days
Refrigerated: 7 days
Frozen: 28 days
Reject Criteria (Eg, hemolysis? Lipemia? Thaw/Other?)
Gross hemolysis
Methodology
Chemiluminescence (CL)
Setup Schedule
Tuesday-friday: PM saturday: AM Tuesday-saturday
Report Available
2 days
Reference Range
Adult Male 12.7-25.1 ug/mL
Adult Female 13.5-30.9 ug/mL
Pediatric
3-8 Years 16.1-24.2 ug/mL
9-13 Years 12.5-25.8 ug/mL
14-17 Years 9.8-23.7 ug/mL
Adult Female 13.5-30.9 ug/mL
Pediatric
3-8 Years 16.1-24.2 ug/mL
9-13 Years 12.5-25.8 ug/mL
14-17 Years 9.8-23.7 ug/mL
Clinical Significance
Thyroxine-binding globulin (TBG), a glycoprotein produced in the liver, binds both thyroxine (T4) and triiodothyronine (T3) with high affinity. Because TBG accounts for 76% of plasma protein thyroxine-binding activity, an increase or decrease in its circulating level alters total concentrations of T4 and T3 in blood, leading to potential confusion with true thyroid gland dysfunction. A number of diseases and medications, as well as inherited alterations in TBG gene expression, can change the serum TBG concentration. Measurement of TBG is useful in distinguishing quantitative TBG derangements from thyroid dysfunction. This analyte is elevated with estrogen therapy (especially oral contraceptive agents), during pregnancy and or hepatitis. Serum TBG may be decreased in cirrhosis, in the nephritic syndrome and by androgens.
Performing Laboratory
| Quest Diagnostics Nichols Institute-Chantilly VA |
| 14225 Newbrook Drive |
| Chantilly, VA 20151-2228 |
