RESUMEN
The aim of this study was to determine whether or not the titre of thyroid-stimulating hormone receptor antibody with stimulating [TRAb-S] activity changes in patients with Graves' disease [GD] or toxic multinodular goitres [TMNG] 3 months after treatment with sodium iodide [131I]. Subjects and Serum specimens were obtained from 21 hyperthyroid patients [15 with GD and 6 with TMNG] at a median 0.5 months before and 3 months after 131I treatment using a standard ablative dose of 555 MBq. TRAb-S activity was measured in a sensitive and specific luminescent bioassay employing the lulu cell line and expressed as a stimulation index [SI; normal 1.5]. The mean TRAb-S in the GD patients was 2.72 SI [95% CI: 1.51-4.03] 0.5 months before administration of 131I and 3.98 SI [95% CI: 1.20-6.76] 3 months after administration of 131I. The difference was not statistically significant at p < 0.8. It was not elevated in the TMNG patients before [0.57 SI; 95% CI: 0.41- 0.73] and after [1.00 SI; 95% CI: 0.74-1.26] treatment either. Conclusions: Radioiodine therapy for GD or TMNG did not induce a significant change in TRAb-S activity at 3 months after treatment with 131I, probably due to effective antithyroid therapy or the timing of samples