Serum triiodothyronine in solitary autonomous nodules of the thyroid

Seventeen patients with solitary autonomous nodules of the thyroid were studied. Eight had clinical features of hyperthyroidism though in some the clinical manifestations were mild. The serum T3 concentration was elevated in all patients with hyperthyroidism but the serum T4 and free thyroxine index were within the normal range in five. All patients with hyperthyroidism subsequently responded to treatment. These findings suggest a high incidence of preferential T3 hypersecretion in hyperthyoidism associated with solitary autonomous thyroid nodule. A further nine patients with single autonomous nodules were clinically euthyroid with normal serum T3 and T4 concentrations and remained euthyroid from 6 to 24 months on serial review.