IgG4 level in thyroid diseases

Introduction and Aim: IgG4 is an auto antibody that is synthesized as a result of stimulation of B lymphocytes with antigens and causes inflammation and dysfunction in many organs in the body and forms the basis of IgG4-related diseases. Another organ where IgG4-related diseases are seen is the thyroid gland. We aimed to measure the IgG4 level of thyroid gland diseases, to observe their clinical effects and to learn the frequency in our country. Materials and Methods: Patients who applied to Manisa Celal Bayar University Hospital Endocrinology and Metabolic Diseases polyclinic between 22/04/2021 and 18/11/2021 were included in our study. Demographic, history, family history and drug use history of the patients were noted. IgG4 and other laboratory parameters were checked. Ultrasonography results in the system were noted. Results: A total of 199 patients, 143 women (72%) and 56 men (28%), were included in our study. The median age of the patients was 44.48 ± 15.02 years, and the median time of diagnosis was 4 (3.5-5.5) years. The number of patients with IgG4 ≥ 135 mg/dl was 35 (17.6%), and the number of patients with IgG4 / IgG ≥ 8% was 56 (28.1%). There was no statistically significant difference between IgG4 and IgG4 / IgG levels of Graves' disease, Hashimoto's thyroiditis, thyroid nodule and control group. In Graves' patients, fT3, fT4 and Hertel scores were statistically significantly higher in groups with IgG4 ≥ 135 mg/dl and IgG4 / IgG ≥ 8%. No statistically significant difference was found in the Hashimoto thyroid group. In the control group, the IgG4 level was found to be much higher than the rates in the literature. Conclusion: In our study, no statistically significant difference was found when the 4 groups were compared with each other in terms of IgG4 and IgG4 / IgG levels. It has been thought that IgG4 may have an effect on thyroid hormone elevation and the severity of ophthalmopathy in Graves' disease. Further studies are needed in the Turkish population in terms of IgG4 positivity, which was detected at a very high rate in the control group compared to the literature. Key words: IgG4, IgG4/IgG, Graves, Ophthalmopathy, Turkey