THYROTROPIN-RECEPTOR ANTIBODIES, IMMUNOGLOBULIN E AND ANTINUCLEAR ANTIBODIES IN PATIENTS WITH GRAVES' DISEASE AND GRAVES' ORBITOPATHY.

Abstract

Thyrotropin-receptor antibodies (TRAb) are biomarkers of Graves' disease (GD) and Graves' orbitopathy (GO). Elevated immunoglobulin E (IgE) and antinuclear antibodies (ANA) were also found in GD patients. We aimed to assess TRAb, IgE and ANA in GD and GO patients and to evaluate the relationship between the immunological markers and smoking. This was a comparative cross-sectional study carried out in a single tertiary care center from June 2018 to January 2020. A total of 103 GD patients (mean age 51.2, 84 females) were divided into three subgroups: moderate-to-severe GO (n=36), mild GO (n=32) and "only GD" subgroup (n=35). Forty healthy controls (HC) (mean age 51.2, 36 females) were also included. TRAb were measured by a thyrotropin-binding inhibitory immunoglobulin (TBII) assay in GD patients; IgE and ANA - by an enzyme-linked immunosorbent assay in all subjects. GD patients had higher IgE-positivity rate (p=0.04) and similar ANA-positivity compared to HC. Moderate-to-severe GO subgroup had the highest TBII (p<0.01), the lowest TBII-negativity rate (p<0.01) and the highest ANA-positivity rate (p=0.03) and was the only subgroup whose IgE-positivity rate was significantly higher than HC (25% vs. 7.5%). Mild GO and "only GD" patients had comparable TBII, TBII-negativity rate, IgE and ANA.Both GO subgroups had significantly higher smoking rate than "only GD" patients. Smoking was positively associated with IgE positivity (φ=0.22, p=0.03), and negatively with TBII negativity rate (φ=-0.24, p=0.02). GD patients exhibit different immunological patterns depending on the presence and severity of GO. Smoking might be just one of the factors responsible for the clinical and immunological variety of GD. Further studies are needed.