Serum TBG level

Alternative names:

serum thyroxine binding globulin; TBG level

Normal values:

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), then normal values may range from 10 mcg/100 ml to 24 mcg/100 ml.

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

Note: mcg/ml = microgram per milliliter

What abnormal results mean:

Elevated TBG levels may indicate:

• pregnancy (TBG levels are normally elevated during pregnancy)
• neonatal status (TBG levels are normally elevated in neonates)
• hypothyroidism
• liver disease
• acute intermittent porphyria

Decreased TBG levels may indicate:

• hyperthyroidism
• acromegaly
• surgery (from the subsequent stress)
• acute illness
• malnutrition (from the low levels of blood protein)
• nephrotic syndrome