Objective To investigate the level of the thyrotropin recepter antibody(TRAb) in healthy people and patients with different types of thyroid disease, and discuss its clinical significance.

Methods Recombinant human thyroid stimulating hormone receptor(TSHR)-ecd N-terminal fragment was used in N method and C-terminal fragment was used in C method as antigens respectively. The serum level of TRAb was measured in 89 healthy people and 254 patients with different types of thyroid disease respectively. The serum levels of TRAb comparison and positive rates comparison between groups were tested by analysis of variance and chi-square test respectively.

Results The result of N method:the 405 nm light absorption value(x±s) in healthy people was 0.511±0.135 with a cut-off value(x±2s) of 0.789. The positive rate was 4.5%(4/89). The 405 nm light absorption value(x±s) in patients with incipient Graves(diffuse toxic goiter) and Hashimoto thyroiditis with hypothyroidism was 0.95±0.30, 0.61±0.22 respectively, which was higher than that in healthy people(F=2.4851 and 2.0763, both P < 0.05). The positive rate in incipient Graves disease, Graves disease with treatment, Graves disease patients in convalescence stage and Hashimoto thyroiditis with hypothyroidism was 73.2%, 55.9%, 32.1%, 45.0%, respectively. There were significant differences between the above groups and the normal control group(χ²=68.55, 56.45, 20.71 and 25.51, all P < 0.05). The positive rate was significantly higher in incipient Graves disease patients than Hashimoto thyroiditis with hypothyroidism patients(χ²=4.63, P < 0.05). There was significant difference in the positive rate between incipient Graves disease and Graves disease patients in convalescence stage(χ²=15.94, P < 0.05). The result of C method:the 405 nm light absorption value(x±s) in healthy people was 0.507±0.142 with a cut-off value(x±2s) of 0.791. The positive rate was 3.4%(3/89). The 405 nm light absorption value(x±s) in Hashimoto thyroiditis with hypothyroidism patients and incipient Graves disease patients was 1.18±0.25, 0.78±0.25, respectively, which was significantly higher than that in healthy people(F=3.8164, 2.4539, P < 0.05). The positive rate in Hashimoto thyroiditis with hypothyroidism, incipient Graves disease, Graves disease with treatment, Graves disease patients in convalescence stage was 75.0%, 46.3%, 23.6%, 16.1%, respectively. There were significant differences among the above groups and the normal control group(χ²=66.34, 36.87, 15.79, 7.30, all P < 0.05). The positive rate was significantly higher in Hashimoto thyroiditis with hypothyroidism than other groups(χ²=4.48, 19.70, 23.68, all P < 0.05).

Conclusions The N method and C method had important significance for detecting the serum level of TRAb in Graves disease and Hashimoto thyroiditis with hypothyroidism. It may be used in clinical diagnosis, treatment and curative effect evaluation for Graves disease and Hashimoto thyroiditis with hypothyroidism.