Endocrinology Book

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Thyroxine Binding GlobulinAka: Thyroid Binding Globulin, TBG

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  1. 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
  2. Interpretation
    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)
  3. 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
  4. 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)

Thyroxine-Binding Globulin (C0087090)

ConceptsAmino Acid, Peptide, or Protein (T116) , Biologically Active Substance (T123)
EnglishTBG, Thyroxin-binding globulin, Thyroxine binding glob., Thyroxine binding globulin, Thyroxine binding globulin -RETIRED-, Thyroxine binding globulin-TBG, Thyroxine-Binding Globulin
Spanishglobulina fijadora de T4, globulina fijadora de tiroxina, globulina fijadora de tiroxina - RETIRADO -
Parent ConceptsSerpins (C0036764), Binding Protein (C0242210), Ambiguous concept (C1274012)
SourcesLNC, MSH, MTH, SCTSPA, SNOMEDCT
Derived from the NIH UMLS (Unified Medical Language System)



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