Thyroxine-binding globulin (TBG) Thyroxine-binding globulin (TBG) is a high-affinity serum binding protein for the thyroid hormones thyroxine (T4) and triiodothyronine (T3) and is one of three transport proteins (along with transthyretin and serum albumin) responsible for circulating these proteins in the bloodstream. Because TBG accounts for 76% of plasma protein thyroxine-binding activity, an increase or decrease in its circulating level alters the total concentrations of T4 and T3 in the blood, leading to potential confusion with true thyroid gland dysfunction. TBG deficiency is a nonharmful condition that can either be acquired or genetically inherited. The only known complications associated with TBG are those that could result from erroneously administered treatment if TBG deficiency is misdiagnosed as another disorder. Elevated TBG levels are associated with influences such as pregnancy, genetic predisposition, oral contraceptives, and estrogen therapy. TBG levels can decrease with androgenic or anabolic steroids, large doses of glucocorticoids, hypoproteinemic states, liver disease, nephrotic syndrome, and congenital TBG variants. Measurement of TBG is useful in distinguishing quantitative TBG derangements from thyroid dysfunction. TBG assays are typically quantitative sandwich ELISAs.
Reagents for Immunoassay Development
MAb to TBG • Affinity Constant: 1 x 10 MAb to TBG • >90% pure (SDS-PAGE)
Suitable for use in ELISA
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