Serum TBG level

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Blood test

Serum thyroxine binding globulin; TBG level

Normal values vary somewhat from laboratory to laboratory, and depend on which method is used to evaluate the sample. If electrophoresis is used, results are reported in terms of T4 binding capacity (the binding capacity of the thyroid hormone T4), and normal values may range from 10 mg/100 ml to 24 mg/100 ml.

If radioimmunoassay is used to evaluate the sample, then a normal range of 1.3 to 2.0 mg/100 ml can be expected.

Other than problems with your thyroid gland, elevated TBG levels may indicate:

• Pregnancy (TBG levels are normally elevated during pregnancy)
• Hypothyroidism
• Liver disease
• Acute intermittent porphyria
• TBG levels are normally elevated in newborns

• Hyperthyroidism
• Acromegaly
• Stress from surgery
• Acute illness
• Malnutrition (from the low levels of blood protein)
• Nephrotic syndrome

Review Date: 04/29/2005
Reviewed By: Frank A. Greco, M.D., Ph.D., Director, Biophysical Laborartory, The Lahey Clinic, Burlington, MA. Review provided by VeriMed Healthcare Network.