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

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 ¹³¹I 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 ¹³¹I therapy using the Marinelli-Quimby formula. The first three months after ¹³¹I 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 ¹³¹I therapy (P < 0.05). After 6 months, patients with lighter thyroid weight, shorter ATD treatment duration before ¹³¹I 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 ¹³¹I is an effective therapy for GD. Even if over time, the occurrence of hypothyroidism may ultimately depend on the patients' radiosensitivity to ¹³¹I 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.