Objective: To evaluate the distribution and significance of IgG subclasses of antithyroglobulin antibody in sera from patients with Hashimoto thyroiditis.
Methods: Sera from 112 patients with Hashimoto thyroiditis were collected and patients were divided into 3 groups, i. e. hypothyroidism, subclinical hypothyroidism and euthyroidism. Antigen specific ELISA was used to detect the distribution of IgG subclasses of antithyroglobulin antibody.
Results: The positive rates of IgG subclasses of TgAb were IgG1 90.2%, IgG2 58.0%, IgG3 19.6% and IgG4 87.5% respectively. The mean geometric titers of IgG1 in sera from patients with hypothyroidism and subclinical hypothyroidism were 1: 450.8 and 1: 245.5 respectively, both being significantly higher than that with euthyroidism (1:8.7, P < 0.01). The mean geometric titers of IgG2 in sera from patients with hypothyroidism and subclinical hypothyroidism were 1: 37.3 and 1: 3.2 respectively, both being also significantly higher than that with euthyroidism (1: 0.2, P < 0.01 and P < 0.05 respectively) and that with hypothyroidism was significantly higher than that with subclinical hypothyroidism (P < 0.05).
Conclusion: The distribution of IgG subclasses of antithyroglobulin antibody in sera from patients with Hashimoto thyroiditis was predominantly IgG1, IgG2 and IgG4. High titers of IgG1 and IgG2 implicated the possibility of development from subclinical hypothyroidism to overt hypothyroidism.