Induction of stimulating thyrotropin receptor antibodies after radioiodine therapy for toxic multinodular goitre and Graves' disease measured with a novel bioassay

131I-Induced Graves' disease in patients treated for toxic multinodular goitre: systematic review and descriptive analysis

BACKGROUND

Graves' disease (GD) arising after the treatment of toxic multinodular goitre (TMNG) with radioiodine has long been described but it remained unclear whether GD was in fact iodine induced, its incidence, risk factors, natural history and treatment outcomes.

METHODS

A systematic search using The Cochrane Library, Medline and PubMed Central allowed the pooling of data from 3633 patients with thyroid autonomy, 1340 patients with TMNG, to fill gaps in knowledge, regarding the clinical expression of iodine-induced GD (131I-IGD) in adults.

RESULTS

131I-IGD developed in 0-5.3% of those with thyroid autonomy (first year) and in 5-5.4% of those with TMNG, 3-6 months after treatment. Patients with toxic adenoma were less affected. 131I-IGD was more common in patients with pre-treatment direct or indirect signs of autoimmunity: positive anti-TPO (p < 0.05), glandular hypoechogenicity, TRAbs within reference range, diffuse uptake on 99mTc-pertechnetate scans (p < 0.05), findings that may increase the risk tenfold. 131I-IGD manifested 3 months after 131I, justifying 15.4-29% of cases of relapse. The rate of spontaneous remission was 17-20% (6 months) and the rate of relapse after a second 131I treatment 22-25%. The use of an uptake-based administered 131I activity led to a greater proportion of euthyroid patients (78% compared to 25-50% with the mass-based approach).

CONCLUSIONS

GD may be triggered by 131I. The incidence of the condition is low. Several risk factors were consistently identified; some have shown to raise the risk significantly. 131I-IGD seems more treatment resistant than iodine-independent GD and the best resolution rates were achieved with uptake-based selected iodine activities.

Immunization with thyroglobulin induces Graves'-like disease in mice

We immunized AKR/N mice with bovine thyroglobulin (Tg) once every 2 weeks and monitored their time-dependent changes in (125)I uptake activity in the thyroid glands. After 3 months, anti-Tg antibody was positive in all sera from the immunized mice. Serum free tri-iodothyronine (T(3)) and free thyroxine (T(4)) levels in the immunized mice (n=6) were significantly higher than those in the saline injected (control) mice (n=6). Neck counts as well as scintigraphy of the thyroid glands revealed that iodide uptake activity of the immunized mice was not suppressed, but was instead higher than that of the control mice. Two of the six immunized mice showed extremely high iodide uptake activity. The thyroid glands of these two mice were diffusely enlarged and the height of the epithelial cells was also increased. In addition, two mice with high iodide uptake activity produced a high titer of thyroid-stimulating antibody. Additional experiments showed that 4 out of 11 AKR/N mice and 3 out of 10 C57BL6 mice immunized with Tg had high serum free T(3)/free T(4) levels, high (125)I uptake activity of the thyroid, and positive thyroid-stimulating antibody activity. Diffuse goiter, thyrotoxicosis, high iodide uptake activity, and positive thyroid-stimulating antibody are the characteristics of Graves' disease. Thus, these mice exhibit the symptoms of Graves' disease. These results suggest that immunization with Tg induces Graves'-like disease in mice and that our methods will provide a new animal model of Graves' disease.