J Korean Soc Endocrinol.  1997 Jun;12(2):194-206.

Changes in Properties of Thyrotropin Receptor Antibodies Following Radioiodine Treatment in Patients with Graves' Disease

• Kim WB
• Chung HK
• Cho BY
• Lee HK
• Koh CS
• Park DJ
• Oh YS

Abstract

BACKGROUND
It has been suggested that thyroid stimulation blocking antibody (TSBAb) is involved in the development of early hypothyroidism after radioiodine treatment in patient with Graves disease. However, previous studies have reported the effect of radioiodine treatment on overall changes of TSH receptor antibodies without detailed observation of changes in properties of TSH receptor antibodies. The aim of this study is to evaluate the effect of radioiodine treatment on thyroid stimulation antibody (TSAb) or on thyroid stimulation blocking antibody (TSBAb) activities and to see whether the appearance of TSBAb after radioiodine treatment is involved in the development of early hypothyroidism in patients with Graves disease.
METHODS
The activities of TSAb, TSBAb were measured serially with human TSH receptor transfected Chinese hamster ovary (CHO) cells in 36 patients with Graves disease who received 131I treatment. In addition to the wild type TSH receptor-expressing cells, we used a chimeric receptor that 90-165 amino acid residues were substituted by those of rat LH/CG receptor (Mc2) for measurement of TSBAb without interference by the presence of TSAb and for evaluation of TSAb epitope spreading. We evaluated the association of early hypothyroidism after 131I treatment with changes of various immunologic parameters.
RESULTS
In 14 (39%) of 36 patients, TSBAb activities were present in their sera before or after 131I treatment. Four of them had TSBAb activities before 131 treatment, and 12 newly acquired TSBAb activities after 131I treatment. The existence of TSBAb was not associated with the development of early hypothyroidism after 131I treatment but with low TSAb activities before 131 treatment, high thyroidal uptake of 131I given and with old age. The phenomena of epitope spreading measured by TSAb with Mc2 mutant clone before and after 131I treatment was not infrequent, but it had no clinical relevance.
CONCLUSION
These results suggest that the existence of TSBAb may be not a major factor in the development of early hypothyroidism after radioiodine treatment in Graves disease. Other factors such as TSAb activities before radioiodine treatment, the efficiency of thyroidal uptake of 131I or old age are associated with the development of early hypothyroidism.

MeSH Terms

Animals
Antibodies*
Clone Cells
Cricetinae
Cricetulus
Female
Graves Disease*
Humans
Hypothyroidism
Ovary
Rats
Receptors, Thyrotropin*
Thyroid Gland
Thyrotropin*
Antibodies
Receptors, Thyrotropin
Thyrotropin