Changes in serum thyroid hormone, thyrotropin and thyroglobulin concentrations during thyroxine therapy in patients...

We studied the effect of therapy with 0.1 mg/day T4 for 3 months on goiter size in 49 patients with solitary thyroid nodules. The nodule volume in 18 patients (responders) decreased by more than 50%. In this group the mean serum thyroglobulin (Tg) levels decreased significantly (from 425 to 61 micrograms/L; P less than 0.01). In the nonresponders the mean serum Tg levels did not change significantly (145 vs. 250 micrograms/L). The mean serum T4, free T4, free T3, and rT3 concentrations increased significantly in both groups during T4 therapy, serum T3 levels did not change, and serum TSH decreased. These findings demonstrate that serum Tg levels decrease when T4 therapy is effective. Thus, serum Tg measurements may prove a useful indicator of the efficacy of T4 therapy in patients with solitary nodules.