Thyroid related
Thyroid binding globulin (TBG)

Topic Completed: 1 March 2011

Revised: 31 December 2018, last major update March 2011

Copyright: (c) 2002-2016,, Inc.

PubMed Search: Thyroid binding globulin [title]

Nat Pernick, M.D.
Page views in 2018: 46
Page views in 2019 to date: 82
Cite this page: Pernick N. Thyroid binding globulin (TBG). website. Accessed September 19th, 2019.
Definition / general
  • Deficiency does not cause thyroid disease by itself
  • Increases / decreases cause increase / decrease in total T3 and T4
  • However, free T3 and T4 are unchanged
  • Produced in liver
  • Major carrier protein for T3 and T4
  • Has highest affinity, but lowest concentration of the carrier proteins
  • Other thyroid carrier proteins are transthyretin and albumin, which have lower affinity but higher concentration
  • Interpreting T3 and T4 levels that do not match clinical findings or other laboratory results
    • For example, total T3 and T4 levels are very low, TSH is normal, free T3 and T4 are normal, patient is clinically euthyroid

  • Chemiluminescence immunoassay

Reference range
  • 13 - 39 μg/dL (150 - 360 nmol/L)

High values
  • Inherited abnormalities, drugs (clofibrate, estrogens, 5-FU, heroin/methadone), hepatitis, pregnancy, idiopathic)

Low values
  • Inherited abnormalities, drugs (androgens, glucocorticoids), liver failure, malnutrition, nephrotic syndrome, idiopathic)
Additional references
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