The present study was undertaken to determine whether thyroid hormone affects serum adiponectin levels in the patients with Basedow disease. Sixty-four patients with Basedow disease were examined; 32 patients had hyperthyroid state and 32 patients had euthyroid state who had been treated with antithyroid drugs. In addition, 30 age- and sex-matched subjects served as a control. Serum adiponectin, free T4, free T3, thyroid-stimulating hormone, and thyroid-stimulating hormone receptor antibody (TRAb) were measured. Serum adiponectin levels were 12.9+/-1.6 microg/mL in the hyperthyroid state, a value significantly greater than that of 8.2 +/- 0.5 microg/mL in the euthyroid state (P<.05) and that of 8.6+/-0.7 microg/mL in the control subjects (P<.05). Serum adiponectin levels had positive correlations with either of serum free T4 (r=0.453, P<.001), free T3 (r=0.47, P< .001), or TRAb (r= 0.491, P<.001), but not with body mass index. Multiple regression analysis showed TRAb had the strongest contribution to serum adiponectin concentration in the patients with Basedow disease. The present findings indicate that hyper-adiponectinemia is closely associated with increases in serum thyroid hormone levels and TRAb in Basedow disease.