Endocrine Abstracts

Introduction

Thyrotropin-receptor antibodies (TRAb) play a key role in the pathogenesis of Graves’ disease (GD) and Graves’ orbitopathy (GO) and are important for the diagnosis of both diseases. Elevated levels of immunoglobulin E (IgE) and antinuclear antibodies (ANA) were also found in GD patients. Smoking is a risk factor for GD and GO development and GO progression. We aimed to assess the associations between TRAb, IgE and ANA, and the presence and severity of GO and smoking in GD patients.

Material and methods

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 in all GD subgroups by a thyrotropin-binding inhibitory immunoglobulin (TBII) assay. TBII<2 IU/ml were considered negative. All subjects were tested for IgE- and ANA-positivity and were categorized as smokers (current and ex-smokers) and non-smokers according to their smoking habits.

Results

The GD group had significantly higher number of smokers (P<0.01), higher IgE-positivity rate (P = 0.04) and a similar percentage of ANA-positivity compared to HC. The moderate-to-severe GO subgroup had significantly higher TBII (P<0.01) and significantly lower TBII-negativity rate (P<0.01) compared to the other two subgroups. The percentage of positive IgE did not differ significantly between GD subgroups, but the moderate-to-severe GO subgroup was the only subgroup, whose IgE-positivity rate was significantly higher than HC (P = 0.01). The moderate-to-severe GO subgroup also had the highest ANA-positivity rate amongst the three subgroups (P = 0.02). Mild GO and “only GD” patients did not differ significantly in terms of TBII level, TBII-negativity rate, IgE and ANA. Both GO subgroups had significantly higher smoking rate than the “only” GD subgroup (P = 0.01). There was a positive correlation between smoking and TBII (ρ = 0.245, P = 0.02) and between smoking and IgE (ρ = 0.23, P = 0.03).

Conclusions

GD patients exhibit different immunological patterns depending on the presence and severity of GO. Smoking might affect the clinical and immunological manifestations of GD, but is not the only factor involved.