Endocrine Abstracts

The natural history of thyroid eye disease (TED), the most frequent extrathyroidal manifestation of Graves' disease, is not completely understood, nor it is clear whether treatments for concomitant hyperthyroidism can influence it. Neither thionamides nor thyroidectomy appear to be disease-modifying treatments. What about radioiodine (RI) therapy? Results are conflicting, owing to selection bias, nonstandardized ocular evaluation, and the retrospective and uncontrolled features of many studies. Few prospective, randomized and controlled studies are available. In one of them (Bartalena et al., N Engl J Med 1989) 9 of 26 patients (35%) with preexisting TED showed a progression of ocular disease after RI therapy, while this phenomenon did not occur in patients concomitantly given glucocorticoids. In another study from Sweden (Tallstedt et al., N Engl J Med 1992) TED development/progression occurred in 10% of methimazole-treated patients, 16% of those submitted to thyroidectomy and 33% of RI-treated patients (p=0.02 vs other treatments). In a large prospective, randomized and controlled study of 450 Graves' patients (Bartalena et al., N Engl J Med 1998), TED worsened in 23 of 150 RI-treated patients (15%), but in only 3% of methimazole-treated patients; RI-associated TED progression could be prevented by a short course of glucocorticoids. Risk factors for TED progression after RI therapy include: TED preexistence, cigarette smoking, severe hyperthyroidism prior to RI therapy, late correction of post-RI hypothyroidism, high TSH-receptor antibody titers.
In summary: a) RI can cause TED progression; b) TED progression is more likely in high-risk patients, particularly smokers; c) TED worsening can be prevented by concomitant glucocorticoid therapy; d) The described effect of RI is short-term, but it is possible that thyroid ablation following RI may have long-term beneficial effects on TED.