IgG4 serum levels in Graves' orbitopathy

Area of Science:

• Endocrinology
• Immunology

Background:

• Immunoglobulin G4-related disease (IgG4-RD) can affect multiple organs, and a potential link between IgG4, Graves' disease (GD), and Graves' orbitopathy (GO) has been debated.
• Conflicting results exist regarding the association between IgG4 and GO, necessitating further investigation.

Purpose of the Study:

• To investigate the association between serum immunoglobulin G4 (IgG4) levels and Graves' orbitopathy (GO) in patients with Graves' disease (GD).
• To evaluate serum IgG4 concentrations, IgG4/IgG ratio, and their prevalence in relation to GO.
• To explore the correlation between IgG4 and specific eye features or anti-TSH receptor antibodies (TRAbs).

Main Methods:

• A retrospective study involving 297 patients with GD and 152 patients with GO.
• Assessment of serum IgG4 concentrations and IgG4/IgG ratio, with a focus on IgG4 levels ≥135 mg/dL (a threshold for IgG4-RD).
• Analysis of subgroups based on FT3 concentrations to account for potential confounding factors.

Main Results:

• In a relevant subgroup analysis (second and third FT3 quartiles), no significant differences in baseline parameters were observed between patients with and without GO.
• The prevalence of elevated IgG4 levels (≥135 mg/dL) was similar in patients with and without GO (17.9% vs 17.3%).
• No differences were found in IgG4 concentrations, IgG4/IgG ratio prevalence (≥8.0%), or correlations between IgG4 and eye features or TRAb levels.

Conclusions:

• The study suggests that serum IgG4 levels are not associated with Graves' orbitopathy (GO) in patients with Graves' disease (GD).
• These findings indicate that IgG4 may not play a significant role in the pathogenesis of GO within the context of GD.