Serum T3 to T4 ratio in Graves' thyrotoxicosis and subacute thyroiditis

Objective To search for simple and practical parameters(the triiodothyronine/thyroxine ratio)that might allow differentiation between the two entities.Methods Analyzed retrospectively the data of patients in endocrine department of the First Affiliated Hospital of Medical University of Xinjiang from August 2004 to October 2008.Results In comparison between groups,triiodothyronine(T3)/tetraiodothyronine(T4)ratio was higher in group of Graves' disease than in group of subacute thyroiditis.The differences between Graves' disease and subacute thyroiditis group were significant(P0.01).Free triiodothyronine(FT3)/free thyroxine(FT4)ratio was higher in group of Graves' disease than in group of subacute thyroiditis.The differences between Graves' disease and subacute thyroditis group were significant(P0.01).Conclusion Serums T3/T4 is as effective as radioactive iodine uptake for differentiation of destruction-induced thyrotoxicosis(subacute thyroiditis for painless)from Graves' thyrotoxicosis.We also can use it for difference of thyrotoxicosis from various causes.