The TBG Enzyme Immunoassay is a diagnostic test used to measure thyroxine-binding globulin (TBG) levels in serum, plasma, or whole blood. TBG is the primary protein responsible for transporting thyroid hormones (T3 and T4) in the bloodstream, making it an essential factor in assessing thyroid hormone availability. This assay provides insights into thyroid disorders and conditions affecting hormone-binding capacity, such as TBG deficiency or excess.