Serum Immunoglobulin G4 Levels are Elevated in Patients with Graves' Ophthalmopathy

Abstract

Objective Recent studies have shown close association between serum Immunoglobulin G4 (IgG4) levels and forms of autoimmune thyroiditis. However, there are limited data about the relationship between IgG4 and Graves' ophthalmopathy (GO). In the present study, we aimed to determine the possible association between IgG4 and GO.

Design Cross-sectional study.

Patients Sixty-five patients with Graves' disease (GD) and 25 healthy controls were recruited into the study. Thirty-two of these patients had GO.

Measurements Serum IgG4 levels, thyroid functions and thyroid volumes were measured in all participants. Ophthalmological examination including Hertel's exophthalmometer readings (HER), Schirmer's test (ST), 'NO SPECS' classification and clinical activity score evaluation (CAS) were performed to all patients with GD.

Results IgG4 levels were significantly elevated in patients with Graves' disease compared to controls (P = 0.0001). Also, IgG4 levels were significantly higher in patients with and without GO when compared to control subjects (P = 0.0001 and P = 0.002, respectively). Furthermore, IgG4 levels were significantly higher in the GO group compared with GD patients without GO (P = 0.024). IgG4 levels were observed to increase in parallel to CAS. Compared with other GD patients, 15 GD patients with serum IgG4 levels >= 135 mg/dl had higher CAS scores (P = 0.012). None of the factors including, TSH, T3, T4 levels, thyroid volume, HER and ST measurements, affect IgG4 levels as an independent factor.

Conclusion IgG4 levels are evidently increased in patients with GD, and there is a possible relationship between IgG4 and GO. Our results suggest that IgG4 may be helpful in screening GD patients with high risk for GO and may well become a good indicator for the selection of right medication in the future.