Predictive factors influencing hypothyroidism following the radioactive iodine treatment of Graves’ disease in different periods

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In China, due to the risks of hypothyroidism after radioiodine treatment, radioiodine is not commonly used as a first-line treatment. In this study, factors influencing the development of hypothyroidism after 131 I therapy for Graves’ hyperthyroidism were evaluated. This was a retrospective study with a 12-month follow-up. Retrospectively, we investigated 1,264 patients with diagnosed Graves’ disease who received 131 I therapy using the Marinelli-Quimby formula. The first three months after 131 I therapy, hypothyroidism risk was higher among patients with lighter thyroid weight, higher levels of thyroglobulin antibody (TGAb), and shorter durations of Antithyroid drug (ATD) treatment before 131 I therapy ( P < 0.05). After 6 months, patients with lighter thyroid weight, shorter ATD treatment duration before 131 I therapy, and higher iodine intake showed an increased risk of hypothyroidism. ( P < 0.05). After one year, lower 24-h iodine uptake was the only risk factor for hypothyroidism ( P < 0.05). Our results show that 131 I is an effective therapy for GD. Even if over time, the occurrence of hypothyroidism may ultimately depend on the patients’ radiosensitivity to 131 I before treatment. But in the first 3 to 6 months or even one year, we can still take measures to effectively improve the quality of life of patients.