Determining thyroxine-binding globulin (TBG) levels is helpful when total thyroid hormone levels are not correlated with thyroid metabolic status, as is often the case during pregnancy and contraceptive use.
More information
Both thyroid hormones, triiodothyronine (T3) and thyroxine (T4), are found in the blood in two forms. Of these two forms, one is the "free" state, which allows the hormone to be biologically active, while the other is the one that binds to plasma proteins. This test measures the level of thyroxine-binding globulin or thyroid-binding globulin (TBG), the primary protein carrier for T3 and T4. Its measurement provides information to aid in the differential diagnosis of actual thyroid disorders from those associated with changes in TBG levels.
Possible Interpretations of Pathological Values
- Increase: Acute intermittent porphyria, active hepatitis, congenital TBG excess, estrogen-secreting tumors, HIV infection, hypothyroidism, liver disease, neonates, pregnancy, acute thyroiditis. Medications: Clofibrate, estrogen, heroin, methadone, oral contraceptives, phenothiazines
- Decrease: Acromegaly, acute disease, congenital TBG deficiency, hyperthyroidism, low albumin (liver disease), malnutrition, nephrosis, nephrotic syndrome, stress, testosterone-producing tumors. Medications: Androgens, phenytoin, prednisone, salicylates, testosterone, valproic acid
Important Note
Laboratory test results are the most critical parameter for diagnosing and monitoring all pathological conditions. Between 70 to 80% of diagnostic decisions are based on laboratory tests. Correctly interpreting laboratory results allows a doctor to distinguish "healthy" from "diseased."
Laboratory test results should not be interpreted from the numerical result of a single analysis. Test results should be analyzed based on each case and family history, clinical findings, and the results of other laboratory tests and information. Your physician should explain the importance of your test results.
At Diagnostiki Athinon, we answer any questions you may have about the test you perform in our laboratory and contact your doctor to ensure you receive the best possible medical care.
