II. Physiology

  1. Radioimmunoassay of major storage of Thyroid Hormone
  2. TBG binds Thyroid Hormone in circulation
    1. Thyroxine (T4) is 99.97% Protein bound
    2. Triiodothyronine (T3) is 99.7% Protein bound

III. Interpretation: General

  1. TBG effects measurement of total T4 and T3
    1. Increased TBG increases total T4 and T3 measurements
      1. Decreased percent Free T4 and T3
      2. No change in Free T4 and Free T3
    2. Decreased TBG decreases total T4 and T3 measurements
      1. Increased percent Free T4 and T3
      2. No change in Free T4 and Free T3
  2. Labs unaffected by Thyroid Binding Globulin (TBG)
    1. Free Thyroxine Index (FTI)
      1. Calculation based on T3 Resin Uptake
    2. Free Thyroxine (Free T4)
    3. Free Triiodothyronine (Free T3)

IV. Interpretation: Increased TBG (Reduces total T4 and T3 measurements)

  1. Pregnancy
  2. Newborn state
  3. Chronic Active Hepatitis
  4. Biliary Cirrhosis
  5. Infection
  6. Acute intermittent porphyria
  7. Familial hyperthyroxinemia
  8. Drugs
    1. Oral Contraceptives
    2. Estrogens
    3. Tamoxifen
    4. Methadone
    5. Heroin
    6. Perphenazine

V. Interpretation: Decreased TBG (Elevates total T4 and T3 measurements)

  1. Chronic Liver Disease
  2. Obstructive Jaundice or Cirrhosis
  3. Severe systemic illness
  4. Active Acromegaly
  5. Nephrotic Syndrome
  6. Surgical Stress
  7. Medications
    1. Androgens
    2. Salicylates
    3. L-asparaginase
    4. Large doses of Glucocorticoids (Prednisone)

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Related Studies

Ontology: Thyroxine-Binding Globulin (C0087090)

Definition (MSH) A thyroid hormone transport protein found in serum. It binds about 75% of circulating THYROXINE and 70% of circulating TRIIODOTHYRONINE.
Definition (NCI) Thyroxine-binding globulin (415 aa, ~46 kDa) is encoded by the human SERPINA7 gene. This protein plays a role in both binding to and transport of both thyroxine and triiodothyroxine.
Concepts Amino Acid, Peptide, or Protein (T116)
MSH D056825
SnomedCT 123338002, 166320009, 166334009, 88181004, 143682007, 415720002
LNC LP32168-4, LP15897-9, MTHU013300
English Thyroxine-Binding Globulin, TBG - Thyroxine binding globulin, TBG-Thyroxine binding globulin, Serpin A7, Thyroxine Binding Globulin, Thyropexin, Thyroxine-Binding Globulin [Chemical/Ingredient], tbg, thyroxine binding globulin (TBG), thyroxine binding globulin, Thyroxine binding glob., Thyroxine binding globulin-TBG, SERPINA7, Thyroxin-Binding Globulin, T4-Binding Globulin, Thyroxine binding globulin -RETIRED-, TBG, Thyroxine binding globulin, Thyroxin-binding globulin, Thyroxine binding globulin (substance)
French Globuline liant la thyroxine, Globuline fixant la thyroxine, Globuline se liant à la thyroxine, TBG (Thyroxine-Binding Globulin), Globuline de liaison à la thyroxine
German Thyroxinbindendes Globulin
Spanish Globulina de Unión a Tiroxina, globulina fijadora de tiroxina - RETIRADO -, globulina fijadora de T4, globulina fijadora de tiroxina - RETIRADO - (concepto no activo), globulina fijadora de tiroxina, globulina fijadora de tiroxina (sustancia)
Swedish Tyroxinbindande globulin
Czech thyropexin, serpin A7, globulin vázající thyroxin
Italian Globulina legante la tiroxina
Polish Globulina wiążąca tyroksynę
Japanese チロキシン結合グロブリン, サイロキシン結合グロブリン
Portuguese Globulina Ligante de Tireoxina, Globulina Ligada a Tireoxina, Globulina Ligada a Tiroxina, Globulina Ligante de Tiroxina, Globulina de Ligação a Tiroxina