Efficacy of radioactive iodine therapy with concomitant antithyroid drugs in Japanese patients with Graves’ disease: a retrospective observational study

This retrospective observational study included 179 patients with GD who visited the University of Tsukuba Hospital. Propensity score matching (balancing age, sex, thyroid weight, free T4) created comparable groups of 15 patients each: CATD(-) withdrawing ATDs and CATD(+) continuing ATDs during RIT. Cure was defined as hypothyroidism or euthyroidism achieved without ATDs or potassium iodide. Post-matching, the CATD(+) group received significantly higher baseline ATD doses (median 600 vs. 200 mg/day propylthiouracil-equivalent; p < 0.008). The cure rate within 12 months after RIT was significantly higher in the CATD(-) group than in the CATD(+) group (n = 12 [80.0%] vs. n = 4 [26.7%]; p = 0.005). CATD may be associated with a lower cure rate within 12 months compared with standard RIT involving temporary ATD discontinuation. We suggest further prospective studies to confirm the efficacy of radioactive iodine therapy with concomitant antithyroid drugs in high iodine intake country.