Thyroxine Binding Globulin (TBG)


This blood test measures Thyroxine Binding Globulins (TBG) levels. Thyroxine Binding Globulins (TBG) are proteins used to transport thyroid hormones in the bloodstream. This blood test is used to detect levels of thyroid binding globulins (TBG), the major thyroid hormone protein carrier.

TBG affects measurement of total T4 and T3. Elevated levels of TBGs may be indicative of infectious hepatitis or porphyria, while decreased levels of TBGs may indicate various causes of hypoproteinemia, such as nephrotic syndrome, gastrointestinal (GI) malabsorption or malnutrition. Elevated levels of testosterone can lower TBG. Conversely, elevated estrogen raise TBG levels.

Test Preparation For Optimal Results:

If possible, have the lab collected early in the morning or shortly after waking. For comparison purposes, have subsequent labs collected close to the same time.

Disclaimer: Your health care provider should evaluate a deviation from normal ranges.