Suppression of serum thyrotropin with thyroxine in patients with Graves' disease: effects on recurrence of hyperthyroidism and thyroid volume.

Based on findings that thyroxine may have a beneficial effect on the recurrence of Graves' hyperthyroidism, we prospectively studied the effects of a TSH suppressive treatment with thyroxine on the course of Graves' disease in fifty patients with recent onset of hyperthyroidism. After the normalization of serum tri-iodothyronine (T3) and thyroxine (T4) concentrations, one group of patients was randomly assigned to a combined treatment with carbimazole and a TSH suppressive dose of T4 for 12 months, followed by another 12 months of TSH suppressive therapy alone. The other group of patients also received carbimazole for one year, but T4 was only added as indicated to normalize elevated TSH serum concentrations, and patients received no therapy during the second year. By the end of the second year, a relapse of hyperthyroidism had occurred in 43% of the patients with and in 45% of the patients without suppressive T4 treatment. In those patients without a relapse of hyperthyroidism, initial thyroid size significantly (P = 0.01) decreased with time in both treatment groups. However, patients on suppressive T4 treatment tended to have a greater reduction in thyroid volume than patients with normal TSH serum concentrations (P = 0.05). In conclusion, we were unable to detect a preventive effect of exogenous TSH suppression on the recurrence of hyperthyroidism. However, our data suggest that TSH suppressive treatment may have a beneficial effect on thyroid enlargement in Graves' disease.