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TBG (Thyroxine Binding Globulin)

Test Summary

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.

Aliases

  • N/A

Specimen Collection

Special Instructions

N/A

Preferred Specimen

1 mL serum

Minimum Volume

0.5 mL

Instructions

N/A

Patient Preparation

N/A

Storage

Plastic screw-cap vial

Transport Temperature

Room temperature

Specimen Stability

  • Room temperature: 7 days
  • Refrigerated: 7 days
  • Frozen: 28 days

Limitations

N/A

Other Acceptable Specimens

N/A

Unacceptable Specimens

N/A

Order Code

THYBG

EPIC (Premier) Code

LAB386

Includes

N/A

CPT Code

  • 84442

Billing Code

  • 700000

CPT Statement

CPT Statement

Methodology

Immunoassay (IA)

FDA Status

FDA Approved

Physician Attestation of Informed Consent

N/A

Testing Laboratory

Quest Diagnostics Nichols Institute
14225 Newbrook Drive
Chantilly VA, 20153

Reference Range

Adult Male 12.7-25.1 mcg/mL
Adult Female 13.5-30.9 mcg/mL
Pediatric    
  4-6 Years 14.8-32.9 mcg/mL
  7-8 Years 16.3-30.7 mcg/mL
  9-10 Years 15.8-27.4 mcg/mL
  11 Years 15.5-27.4 mcg/mL
  12 Years 14.8-26.2 mcg/mL
  13 Years 13.8-25.2 mcg/mL
  14 Years 12.2-25.2 mcg/mL
  15 Years 10.8-23.8 mcg/mL
  16 Years 10.0-23.8 mcg/mL
  17 Years 8.5-23.1 mcg/mL

Setup Schedule / Expected Turnaround Time

Daily evening; Report available: Same day

Specimen Collection

Special Instructions

N/A

Preferred Specimen

1 mL serum

Minimum Volume

0.5 mL

Instructions

N/A

Patient Preparation

N/A

Storage

Plastic screw-cap vial

Transport Temperature

Room temperature

Specimen Stability

  • Room temperature: 7 days
  • Refrigerated: 7 days
  • Frozen: 28 days

Limitations

N/A

Other Acceptable Specimens

N/A

Unacceptable Specimens

N/A

Billing

CPT Code

  • 84442

Billing Code

  • 700000

CPT Statement

CPT Statement

Result Information

Methodology

Immunoassay (IA)

Testing Laboratory

N/A

Reference Range

Adult Male 12.7-25.1 mcg/mL
Adult Female 13.5-30.9 mcg/mL
Pediatric    
  4-6 Years 14.8-32.9 mcg/mL
  7-8 Years 16.3-30.7 mcg/mL
  9-10 Years 15.8-27.4 mcg/mL
  11 Years 15.5-27.4 mcg/mL
  12 Years 14.8-26.2 mcg/mL
  13 Years 13.8-25.2 mcg/mL
  14 Years 12.2-25.2 mcg/mL
  15 Years 10.8-23.8 mcg/mL
  16 Years 10.0-23.8 mcg/mL
  17 Years 8.5-23.1 mcg/mL

Setup Schedule / Expected Turnaround Time

Daily evening; Report available: Same day