[Significance of combining tests of thyroid autoantibodies in differential diagnosis between Graves's disease and Hashimoto's hyperthyroidism]

Abstract

Objective: To investigate the differential diagnosis between Graves's disease and Hashimoto's hyperthyroidism to improve positive diagnostic rate in Hashimoto's hyperthyroidism, to facilitate proper management.

Methods: Cytological examination was conducted by fine needle biopsy (FNB) on the thyroids of patients with hyperthyroidism diagnosed by clinical data, including 22 cases of Hashimoto's hyperthyroidism, 5 males and 17 females, aged 39 +/- 12, and 49 cases of Graves's disease, 20 males and 29 females, aged 41 +/- 11. Thyroid auto-antibodies-thyroid peroxidase antibody (TPOAb), thyroid microsomal antibody (TMA), thyroglobulin antibody (TGA), thyroid-stimulating hormone receptor antibody (TRAb), and free serum triiodothyronine (FT3), free thyroxin (FT4), and serum thyroid-stimulating hormone (S-TSH) were tested. The correlation between the pathology of thyroid and different autoantibodies and thyroid hormone was analyzed.

Results: TRAb was 42.28 +/- 75.89 in Graves disease group, significantly higher than that in Hashimoto's hyperthyroidism group (5.77 +/- 12.69, P < 0.001). FT3 was 16.13 +/- 9.95, significantly higher than that in Hashimoto's hyperthyroidism group (9.54 +/- 6.76, P < 0.01). In Graves's disease group the positive rates for TRAb, TPOAb, TMA, and TGA were 83.67%, 75.51%, 57.14% and 48.98% respectively. In Hashimoto's hyperthyroidism group, the positive rate for TRAb was 13.64%, and the positive rates for the rest autoantibodies were all 86.36%. The double positive rate of TPOAb and TGA was 86.36% in Hashimoto's hyperthyroidism group, significantly higher than that in Graves's disease group (48.98%). There was a positive association between TRAb and FT3, and between diffuse and symmetric increased size of thyroid and FT3 TRAb.

Conclusion: Comprehensive analysis of TRAb, TPOAb, TGA, and FT3 is helpful to the differential diagnosis between Graves's disease and Hashimoto's hyperthyroidism.