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Thyroxine Binding Globulin (TBG)

Order Code CH493
Turnaround Time 48 hours
Test Includes

Thyroxine Binding Globulin (TBG)

Specimen Requirements
Specimen Source
Transport Container
(Specimen Container)

SST (Tiger Top)

Preferred Specimens
Minimum Volume (uL)
0.5 mL
Collection Instructions
(Transport Temperature)
Transport at Room Temperature
Specimen Stability
Temperature Period
Room temperature 7 days
Refrigerated 7 days
Frozen 28 days
Reject Criteria

Gross hemolysis

Test Details
mmunoassay (IA
Clinical Significance

TBG (Thyroxine Binding Globulin) – 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.

Reference Ranges

Adult Male:
12.7-25.1 mcg/mL

Adult Female:
13.5-30.9 mcg/mL

14.8 – 32.9 mcg/mL (4-6 Years)
16.3 – 30.7 mcg/mL (7-8 Years)
15.8 – 27.4 mcg/mL (9-10 Years)
15.5 – 27.4 mcg/mL (11 Years)
14.8 – 26.2 mcg/mL (12 Years)
13.8 – 25.2 mcg/mL (13 Years)
12.2 – 25.2 mcg/mL (14 Years)
10.8 – 23.8 mcg/mL (15 Years)
10.0 – 23.8 mcg/mL (16 Years)
8.5 – 23.1 mcg/mL (17 Years)