Suppressive Therapy with Levothyroxine for Solitary Thyroid Nodules

Thyroid nodules are present in up to 50 percent of adults in the fifth decade of life. Patients are often treated with thyroxine in order to reduce the size of the nodule, but the efficacy of thyrotropin-suppressive therapy with thyroxine remains uncertain. In this study, 53 patients with a colloid solitary thyroid nodule confirmed by biopsy were randomly assigned in a double-blind manner to receive placebo (n = 25) or levothyroxine (n = 28) for six months. Before treatment, pertechnetate-99m thyroid scanning showed that 22 percent of the nodules were functional, 25 percent hypofunctional, and 53 percent nonfunctional. High-resolution (10-MHz) sonography was used to measure the size of the nodules before and after treatment. Suppression of thyrotropin release was confirmed in the levothyroxine-treated group by the administration of thyrotropin-releasing hormone; thyrotropin release was normal in the placebo group. Six months of therapy did not significantly decrease the diameter or volume of the nodules in the levothyroxine group as compared with the placebo group. We conclude that the efficacy of levothyroxine therapy in reducing the size of colloid thyroid nodules is not apparent within six months, despite effective suppression of thyrotropin.