[The relationship between serum thyroid autoantibodies, iodine intake, development and prognosis of Graves' disease]

To investigate the relationship of thyroid autoantibodies including serum thyroid stimulating antibody (TSAb), thyroid stimulation blocking antibody (TSBAb) and iodine intake with the development and prognosis of Graves' hyperthyroidism.

A total of 63 subjects with overt hyperthyroidism were screened out from 3 Chinese rural communities with different iodine intakes at first survey. Serum TSAb, TSBAb, thyrotropin binding inhibitory immunoglobulin (TBII), thyroid peroxidase antibody (TPOAb) and thyroglobulin antibody (TGAb) were detected. The patients were followed up 2 years later. TSAb and TSBAb were measured with recombinant human thyrotropin receptor (rhTSHR)-Chinese hamster ovary cell (rhTSHR-CHO cell) bioassay.

At the first survey, the prevalences of positive TSAb, TBII and TSBAb were found in 80.9%, 61.7% and 6.4% of the patients with Graves' disease respectively. TSAb and/or TBII were positive in 91.5% of the patients. The consistent rate of TSAb and TBII was 59.6% in the cases. All indexes mentioned above were higher in the patients than in healthy controls. Positive correlations were found between TSAb and TBII (r = 0.407), TSAb and thyroglobulin (r = 0.301), TSAb and thyroid volume (r = 0.317) respectively. The prevalence of positive TSAb (91.7%) in Graves' patients in iodine excessive area are significantly higher than those in iodine mildly deficient area (66.7%). The positive rates and the titers of TBII, TPOAb and TGAb were not different statistically among the patients in the three communities. At follow-up, the patients with Graves' hyperthyroidism were classified into euthyroid group (G1) and hyperthyroid group (G2) according to their outcomes of the disease. The TSAb titers and the thyroid volume in the cases of G1 decreased significantly, whereas the patients with highly positive TPOAb titers in the first survey and the follow-up were hard to become euthyroid and TSAb may be the secondary factor influencing the thyroid as compared with TPOAb.

TSAb is more significant than TBII in diagnosing and predicting the outcomes of Graves' hyperthyroidism. The application of both TSAb and TBII could raise the positive rates of thyrotrophin receptor antibody tests. TSAb, TPOAb titers and thyroid volume were factors influencing the prognosis of Graves' hyperthyroidism.