BACKGROUND: There are case reports in the literature that patients occasionally develop immunogenic hyperthyroidism 2 to 14 months following iodine-131-therapy of focal, non-immunogenic, autonomous thyroid nodules with a prevalence between 0.05 and 2.5%. Purpose of this multicenter evaluation was to assess the appearance of this phenomenon in a larger patient population. PATIENTS AND METHODS: So far 2867 patients out of 4 university hospitals are included in our study focusing on the appearance of pathologically elevated levels of thyrotropin-receptor-antibodies (TRAb) combined with hyperthyroidism following iodine-therapy. Records of the patients were screened for pre- and post-therapeutic biochemical tests, scintigraphic uptake patterns and ultrasound findings of the thyroid. RESULTS: Nineteen of 2867 patients with pretherapeutically scintigraphic "hot nodules" developed recurrent hyperthyroidism suggestive for immunogenic genesis 2 to 12 months following iodine-131-therapy (elevated TRAb-levels, homogeneous uptake in Tc-99m-pertechnetate scans). Pretherapeutically, 9 of these patients presented with a strictly focal scintigraphic uptake-pattern, 10 cases with a mixed disseminated-focal pattern. Because of missing pretherapeutic TRAb-tests in 8/9 patients presenting with a strictly focal scintigraphic uptake pattern, postradiogenic immunogenic hyperthyroidism could be reliably assessed in 1 case only. CONCLUSION: One could speculate that iodine-131-therapy may stimulate immunogenic mechanisms finally leading to immunogenic hyperthyroidism. Posttherapeutically observed hyperthyroidism following iodine-treatment might be based on an exacerbation of a preexisting--clinically not relevant/detectable--immunothyropathia. Also pretherapeutic TRAb-negative immunogenic hyperthyroidism could not be definitely excluded. Our multicenter data collected in a large patient population show similar results to the case reports of immunogenic hyperthyroidism following iodine-131-treatment in smaller populations. Therfore, the occurrence of this phenomenon plays a minor role regarding to its prevalence. Therapeutical consequences in treatment of functional thyroid autonomy are not recommended.
BACKGROUND: There are case reports in the literature that patients occasionally develop immunogenic hyperthyroidism 2 to 14 months following iodine-131-therapy of focal, non-immunogenic, autonomous thyroid nodules with a prevalence between 0.05 and 2.5%. Purpose of this multicenter evaluation was to assess the appearance of this phenomenon in a larger patient population. PATIENTS AND METHODS: So far 2867 patients out of 4 university hospitals are included in our study focusing on the appearance of pathologically elevated levels of thyrotropin-receptor-antibodies (TRAb) combined with hyperthyroidism following iodine-therapy. Records of the patients were screened for pre- and post-therapeutic biochemical tests, scintigraphic uptake patterns and ultrasound findings of the thyroid. RESULTS: Nineteen of 2867 patients with pretherapeutically scintigraphic "hot nodules" developed recurrent hyperthyroidism suggestive for immunogenic genesis 2 to 12 months following iodine-131-therapy (elevated TRAb-levels, homogeneous uptake in Tc-99m-pertechnetate scans). Pretherapeutically, 9 of these patients presented with a strictly focal scintigraphic uptake-pattern, 10 cases with a mixed disseminated-focal pattern. Because of missing pretherapeutic TRAb-tests in 8/9 patients presenting with a strictly focal scintigraphic uptake pattern, postradiogenic immunogenic hyperthyroidism could be reliably assessed in 1 case only. CONCLUSION: One could speculate that iodine-131-therapy may stimulate immunogenic mechanisms finally leading to immunogenic hyperthyroidism. Posttherapeutically observed hyperthyroidism following iodine-treatment might be based on an exacerbation of a preexisting--clinically not relevant/detectable--immunothyropathia. Also pretherapeutic TRAb-negative immunogenic hyperthyroidism could not be definitely excluded. Our multicenter data collected in a large patient population show similar results to the case reports of immunogenic hyperthyroidism following iodine-131-treatment in smaller populations. Therfore, the occurrence of this phenomenon plays a minor role regarding to its prevalence. Therapeutical consequences in treatment of functional thyroid autonomy are not recommended.