A Belgian single centre outcome study of radioiodine treatment in adolescents with Graves' disease.

Up to 80% of children/adolescents with Graves' disease (GD) may require second-line treatment with either surgery or radioactive iodine (RAI) therapy after treatment with antithyroid drugs. These interventions aim to induce permanent hypothyroidism, but are not always successful. We aimed to evaluate the initial success rate (within the first year) of RAI treatment and its determining factors as second-line treatment in teenagers with GD. We also assessed the tolerability of RAI therapy and the onset speed of RAI-induced hypothyroidism. We conducted a retrospective chart review of children < 18 years treated with RAI (scaled fixed dose) for GD between January 2007 and December 2022 at the UZ Brussels. Fourteen teenagers treated with RAI were identified. Their ages at time of treatment ranged from 9.8 to 17.3 years, with administered I131 doses between 5.8 and 15.0mCi (median 7.9mCi). All but two patients responded within six months. Thyroxine treatment was started between 4 and 14 weeks (median 9 weeks) after RAI therapy. The time to thyroxine substitution correlated positively with age (Rho = 0.498; p = 0.099) and total I131-dose (Rho = 0.582; p = 0.047). One patient experienced transient RAI induced sialadenitis. None of the patients relapsed during a follow-up period of 1.2 to 13 years. A cure rate of 86% was observed in GD teenagers receiving a second-line RAI treatment, with no major complications. Most patients became hypothyroid within three months, underscoring the importance of early thyroid function monitoring.