1. Department of Nuclear Medicine, Geelong Hospital, Geelong, Victoria 3220, Australia.
Background: Anti-thyroid drugs (ATD) are routinely used in Australian practice as first-line therapy for Graves' hyperthyroidism (GH) prior to 131I (radioiodine) treatment. There is concern that patients who do not receive ATD pre-treatment will develop uncontrolled hyperthyroidism before and after 131I therapy and that 131I therapy without ATD pre-treatment may not be as efficacious as with ATD pre-treatment.
Methods: We reviewed the records of consecutive patients with GH who received 131I over an 18 months period and compared patients who had not received ATD pretreatment with those who had, in respect to outcomes and episodes of uncontrolled hyperthyroidism post treatment. Ninety-three 131I treatments ("episodes") were administered to 82 patients, nine of whom required more than one treatment. Fifty episodes were preceded by pre-treatment ("Group A"), 41 were not ("Group B") and two episodes were associated with unknown pre-treatment status.
Results: There were no significant differences between Groups A and B in respect to; success of treatment, final thyroid status after treatment or episodes of uncontrolled hyperthyroidism Of the 13 patients who required further therapy with either 131I or surgery after their initial 131I episode, there were no differences in terms of pre 131I characteristics or outcomes within this subgroup compared to those who had received ATD prior to 131I and those who had not. None of the 131I episodes led to uncontrolled hyperthyroidism that necessitated hospitalization or the supervised use of ATD following 131I therapy.
Conclusion: The use of ATD prior to 131I therapy did not influence the outcome of 131I therapy in terms of efficacy in this cohort. Neither the incidence nor the time of onset of hypothyroidism following 131I therapy was significantly affected by the use of ATD pretreatment. There were no episodes of uncontrolled hyperthyroidism following 131I treatment. ATD pre-treatment is not a prerequisite for successful 131I therapy.
Keywords: Graves' hyperthyroidism, radioiodine, anti thyroid drugs, Australia