title: Thyroxine may decrease serum thyroxine-binding globulin levels.
abstract: The purpose of this study was to elucidate the influence of thyroxine on the serum thyroxine-binding globulin (TBG) levels. Serum TBG levels were determined in 100 normal people, 100 cases of simple goiter, 50 cases of nodular goiter, 50 cases of Graves' disease and 70 cases of autoimmune thyroiditis (35 cases in the euthyroid state, and 35 cases in the hypothyroid state). The serum TBG levels were 14.3 +/- 0.3 micrograms/ml (mean +/- SE) in the normal control, 14.1 +/- 0.4 micrograms/ml in simple goiters, 14.9 +/- 0.5 micrograms/ml in nodular goiters, 13.0 +/- 0.5 micrograms/ml in Graves' disease, 15.0 +/- 0.6 micrograms/ml in euthyroid autoimmune thyroiditis and 17.4 +/- 0.8 micrograms/ml in hypothyroid autoimmune thyroiditis. The serum TBG levels were significantly decreased in Graves' disease (p less than 0.05) and significantly increased in hypothyroid autoimmune thyroiditis (p less than or equal to 0.01) as compared with the control. Serum TBG levels were determined after treatment by antithyroid drugs in 25 cases of Graves' disease, by thyroxine replacement therapy in 15 cases of hypothyroid autoimmune thyroiditis and by thyroxine suppression therapy in 25 cases of nodular goiter. Serum TBG levels increased significantly after treatment with antithyroid drugs (p less than 0.005) in Graves' disease. Serum TBG levels decreased significantly both after treatment with thyroxine (p less than 0.01) in hypothyroid autoimmune thyroiditis and after treatment with thyroxine (p less than 0.005) in nodular goiter. This evidence supports the conclusion that T4 may decrease serum concentrations of TBG.
authors.forename: J Y
authors.initials: JY
authors.lastname: Lin
authors.forename: S E
authors.initials: SE
authors.lastname: Hwu-Liaw
authors.forename: T C
authors.initials: TC
authors.lastname: Chang
mesh_terms: D000818:Animals; D002417:Cattle; D006111:Graves Disease / Q000097:blood; D006801:Humans; D007037:Hypothyroidism / Q000097:blood; D013967:Thyroiditis, Autoimmune / Q000097:blood; D013974:Thyroxine / Q000097:blood / Q000494:pharmacology*; D013975:Thyroxine-Binding Proteins / Q000032:analysis*
chemical_list: D013975:Thyroxine-Binding Proteins; D013974:Thyroxine