Thyroxine Binding Globulin, Serum

Thyroxine binding globulin (TBG) is a protein produced by the liver that carries thyroid hormones, primarily thyroxine (T4) and triiodothyronine (T3), in the blood. Only a small fraction of thyroid hormones circulates freely, while most are bound to proteins like TBG. The Thyroxine Binding Globulin, Serum test measures how much of this protein is present in the blood, which affects interpretation of total thyroid hormone levels and helps assess hormone transport.

Doctors may recommend this test when there are general symptoms suggestive of thyroid imbalance, such as constipation, dry skin, diarrhea, puffy skin, tiredness, hair loss, weakness, sensitivity to cold or heat, fast heartbeat, weight changes, or irregular periods, particularly when thyroid hormone results (total T3/T4) appear unusual or unclear relative to free hormone levels or the clinical picture. This test is advised for conditions affecting hormone-binding proteins, such as pregnancy, liver disease, nephrotic syndrome, or suspected genetic TBG disorders.

No special preparation is required for the Thyroxine Binding Globulin, Serum test. Inform the doctor about all the medications and supplements currently being taken, as these may affect the test results.

Test result ranges are approximate and may differ slightly between labs depending on the methodology and laboratory guidelines. Do not self-diagnose and always consult a doctor to understand the test results correctly. 

Please note: This is an outsourced test. The sample for this test is collected by TATA 1MG and processed at a NABL accredited partnered lab.