Endocrine Abstracts

Introduction: Radioactive iodine (RAI) has been used to treat hyperthyroidism for over 70 years. Some centres use a fixed dose regimen while others use a calculated dose regimen. Cure rates range between 80% and 100%, with some patients requiring two or more doses. We use the fixed-dose regimen at our centre. We therefore evaluated our cure rates after a single dose of RAI to treat hyperthyroidism.

Methods: We reviewed the medical records of patients who received their first dose of RAI between 2016 and 2021. Patients had telephone follow-up and biochemical assessment every six weeks until six months post-RAI therapy, then every three months thereafter until cured. Patients were deemed cured when they developed persistent hypothyroidism or euthyroidism after a single dose of RAI.

Results: One hundred and thirty-eight patients received their first dose of RAI during the study period. The group had a mean ± standard deviation age of 56.9 ± 15.3 years and included 101 women and 37 men. The median duration of hyperthyroidism was 34 months, and 62% of patients had Graves’ disease. A majority (90%) were on an antithyroid drug prior to RAI therapy. The median (interquartile range) dose of RAI received was 559 (546-577) megabecquerels. Four patients (2.9%) reported adverse events after receiving RAI. Our overall cure rate was 87.7% after a single dose of RAI therapy [96 patients (69.6%) developed hypothyroidism and 25 patients (18.1%) remained euthyroid]. Our one-year cure rate was 84.1%. Furthermore, women had a greater cure rate when compared to men (92% vs 75.7%, P= 0.017).

Conclusions: Our centre had an overall cure rate of 87.7% after a single dose of RAI therapy given to treat hyperthyroidism, and a one-year cure rate of 84.1%. Our results are comparable to that reported at other centres using a similar dosing regimen.