Endocrine Abstracts

Introduction

Radioiodine I-131 (RAI) therapy of Graves’ Disease (GD) affects biological thyroid function, clinical signs of hyperthyroidism (SCH), but also the mass of the thyroid (MT). The aim of our study is to assess the effect of RAI on GD and TM according to biological thyroid function after 6 and 12 months.

Methods

This is a prospective study of 86 patients (mean age 43 ± 11, sex ratio 2.07) referred for RAI therapy of GD. The biological thyroid function was assessed after 6 months and one year of RAI. The patient’s weight, heart rate and thyroid mass were evaluated at 6 months and 12 months. According to the biological thyroid function at 6 and 12 months, the patients are divided into two subgroups: the subgroup of patients who persist in hyperthyroidism (GI) and the patients who achieved remission (eu- or hypo-thyroidism) (GII). We compared the change in weight, heart rate, and thyroid mass after RAI between the two subgroups.

Results

Follow-up after RAI was possible in 66 patients at 6 months and 63 after a year. Hyperthyroidism persists or recurs in 29% of patients at 6 months and 20% at 12 months. We noted weight gain (p <0.0001 at 6 and 12 months), reduction in heart rate (P = 0.003 at 6 months and P <0.0001 at 12 months) and reduction in TM (P <0.0001 at 6 and 12 months) for all patients. Weight gain was significant for both subgroups at 6 and 12 months, but less significant for GI (P = 0.001 vs P <0.0001 at 6 months and P = 0.047 vs P <0.0001 at 12 months ). At 6 months, the reduction in heart rate was significant for GII (P = 0.002) but not significant for GI (P = 0.47). At 12 months, the reduction in heart rate was significant for both subgroups, but less significant for GI (P = 0.008 vs P = 0.005). The reduction in MT was significant for both subgroups at 6 and 12 months, but less significant for GI (P = 0.001 vs P <0.0001 at 6 months and P = 0.007 vs P = 0.0001 at 12 months).

Conclusion

RAI therapy improves SCH and reduces thyroid mass even for the subgroup of patients with persistent hyperthyroidism, but less significantly than the subgroup of patients who achieved remission at 6 and 12 months.