However, no significant differences for rs2294025 and rs7005834 were observed, between the different clinical phenotypes of GD, including gender, Graves' ophthalmopathy (GO), and serum levels of thyrotropin receptor antibody, thyroid peroxidase antibody, and thyroglobulin antibody.
Patients with immunoglobulin G4 levels above the 75th percentile (>237.52 mg/dl, N = 20) were younger at Graves' ophthalmopathy onset (p < 0.001), had higher antithyroid peroxidase antibody (p = 0.01), and anti-thyroglobulin antibody levels (p = 0.006) and required shorter duration of the first methimazole treatment cycle (p = 0.041) than patients with immunoglobulin G4 below the 75th percentile.
The succinate dehydrogenase flavoprotein subunit gene (SDHA) was also significantly up-regulated in GO (P < 0.05), 1.4-fold, while genes encoding the thyroid antigens thyroglobulin, thyroid peroxidase and TSHR were not differentially expressed. qPCR verified up-regulation of CASQ2 and down-regulation BMP7, CD80, IGFBP5, and MYD88 genes in GO.
The nature of the putative autoantigen in Graves' ophthalmopathy (Go) remains an enigma but the sequence similarity between thyroglobulin (Tg) and acetylcholinesterase (ACHE) provides a rationale for epitopes which are common to the thyroid gland and the eye orbit.