Antithyroid drug therapy: predictive parameters

Antithyroid drugs have mainly been used to obtain euthyroidism in patients with chronic hyperthyroidism independent from its etiology and for long-term medical treatment of hyperthyroidism due to Graves' disease. Endocrinologists are faced with the problem of potential side-effects and a high relapse rate (30-50%) after an apparently successful treatment course. Several studies have therefore been undertaken to find parameters for the prediction of outcome of antithyroid drug therapy. Most of the investigated variables have proven rather disappointing as predictors. The strongest investigated predictors are goitre size and the level of thyrotropin receptor antibodies. It may be concluded that patients with very large goitres and high levels of thyrotropin receptor antibodies are unlikely to obtain permanent euthyroidism by treatment with antithyroid drugs, and therefore might benefit from a more destructive therapy (radioiodine or surgery) at an early stage of the disease. For all other patients prediction of outcome is not possible at present and choice of therapy should be based on available studies on high versus low dose antithyroid drug therapy, optimal length of therapy, in all cases with careful consideration of risk of side-effects.