Incidence of radiation-induced Graves? disease in patients treated with radioiodine for thyroid autonomy before and after introduction of a high-sensitivity TSH receptor antibody assay

Abstract

Autoimmune hyperthyroidism may occur several months after radioiodine therapy (RIT) for functional thyroid autonomy. Exacerbation of pre-existing subclinical Graves' disease (GD) has been held responsible for this phenomenon. Determination of TSH receptor antibody using solubilised porcine epithelial cell membranes is insensitive and may have failed to diagnose GD in these patients before RIT. Following the introduction of a more sensitive assay, using the human TSH receptor as an antigen, it has been expected that the incidence of radiation-induced GD after RIT for functional thyroid autonomy will be reduced. In a first group of 1,428 patients treated between November 1993 and March 1997 (group I) we used the porcine TRAb assay to exclude GD, while in a second group comprising 1,408 patients treated between January 2000 and December 2001 (group II), GD was excluded using the human TRAb assay. A matched control group of 231 patients was derived from group II. In group I a total of 15 (1.05%) patients developed obvious or suspected radiation-induced GD, while in group II 17 (1.2%) did so; the interval until development of GD was 8.4 and 8.8 months, respectively, after RIT. Serum anti-thyroid peroxidase levels before RIT were elevated in 36.4% of group I patients and 47.1% of group II patients, but in only 5.6% of the control group. Other non-specific signs of mild immunopathy of the thyroid were seen retrospectively in 73.3%, 64.7% and 16.0% of the patients in these three groups, respectively. In conclusion, the introduction of a high-sensitivity TRAb assay did not reduce the incidence of autoimmune hyperthyroidism occurring late after RIT for functional thyroid autonomy, but mild immunopathy of the thyroid is seen more frequently in these patients and seems to be a predisposing factor in the development of radiation-induced GD.

Wole guzowate olbrzymie — ambulatoryjne leczenie radiojodem

“…In one patient after treatment we observed an increase of TRAb, while a reduction of these antibodies in 6 other patients was noticed. Despite the described TRAb increase following radioiodine therapy for Graves disease [31,32] and in thyroid cancers [33,34], autonomous thyroid disease [35], as well as nontoxic goitre [36], we did not obtain such results. Long observation time, assessment at only two time points, or advanced patient's age may be of importance for these results.…”

Thyroid autoimmunity

“…Similarly, radioiodine treatment of toxic goitre may be followed, years later, by the occurrence of Graves' disease, even Graves' ophthalmopathy [59]. In a different context, children exposed to radiation from Chernobyl showed a greater incidence of thyroid autoantibody positivity, with no increase in the incidence of hypothyroidism [60].…”

Autoimmune thyroid disorders

“…Radioiodine treatment of toxic goiter may be followed by the appearance of GD, even by Graves' ophthalmopathy (GO) [27]. Children exposed to radiation from Chernobyl showed a greater prevalence of thyroid autoantibody [28].…”