Long-term effects of radioiodine on thyrotrophin receptor antibodies in Graves' disease.
OBJECTIVE
Graves' disease is recognized as an organ-specific autoimmune disorder caused by the presence of TSH receptor antibodies. The long-term effects of 131I treatment for Graves' disease on TSH receptor antibodies have not previously been studied. We have measured the TSH-binding inhibitory immunoglobulin (TBII) index and thyroid stimulating antibody (TSAb) activity in patients with Graves' disease following treatment with 131I.


METHODS
A retrospective study.


METHODS
Two hundred and twenty-five patients with Graves' disease who were treated with 131I 1-13 years earlier were studied (1 year: 27 patients; 2-5 years: 42 patients; 6-9 years: 79 patients; 10-13 years: 77 patients).


METHODS
The TBII index was measured as the percentage 125I-TSH bound to pig thyroid membranes and TSAb activity as the amount of cAMP produced by cultured FRTL-5 cells.


RESULTS
TBII was detected in 78% of patients prior to 131I administration. Following 131I administration, the incidence of positive TBII was 85% at the end of the first year decreasing to 40, 19, and 17% at 2-5, 6-9 and 10-13 years, respectively. The frequency of a positive TSAb was 74% at the end of the first year, and also decreased to 49, 27 and 29% at 2-5, 6-9 and 10-13 years, respectively. At more than 2 years after 131I therapy, the frequencies of hyperthyroidism in TBII and TSAb positive patients were 42% (19/45) and 30% (19/63), respectively, which were significantly higher than those in TBII and TSAb negative patients (8%: 12/153 and 8%:11/131, respectively). The frequency of hyperthyroidism after 131I treatment in patients with negative TBII before treatment (7%:2/29) was significantly lower than that (29%:30/102) in patients with positive TBII before treatment.


CONCLUSIONS
These results indicate that (1) the TBII index and TSAb activity decreased over a period of more than 2 years after 131I therapy for Graves' disease, and (2) the TBII index before treatment may influence the long-term outcome of 131I therapy.
Aizawa
Y
Y
Second Department of Internal Medicine, Tohoku University School of Medicine, Sendai, Japan.
Yoshida
K
K
Kaise
N
N
Kaise
K
K
Fukazawa
H
H
Kiso
Y
Y
Mori
K
K
Sayama
N
N
Kikuchi
K
K
Abe
K
K
D000328:Adult; D000368:Aged; D001323:Autoantibodies / Q000032:analysis*; D005260:Female; D006111:Graves Disease / Q000276:immunology* / Q000532:radiotherapy; D006801:Humans; D006980:Hyperthyroidism / Q000209:etiology / Q000276:immunology; D018828:Immunoglobulins, Thyroid-Stimulating / Q000032:analysis; D007457:Iodine Radioisotopes / Q000627:therapeutic use*; D008297:Male; D008875:Middle Aged; D011989:Receptors, Thyrotropin / Q000032:analysis / Q000276:immunology*; D012189:Retrospective Studies; D013997:Time Factors
D001323:Autoantibodies; D018828:Immunoglobulins, Thyroid-Stimulating; D007457:Iodine Radioisotopes; D011989:Receptors, Thyrotropin; C094372:thyrotropin-binding inhibitory immunoglobulin