[Clinical and immunological predictors of Graves' orbitopathy after radioiodine therapy of Graves' disease].

Background: Data on the effect of 131I on the course of Graves' orbitopathy (GO) are contradictory. A number of studies indicate a deterioration in the course of GO against the background of RAIT, in other studies such a connection has not been established. Cytokines that regulate inflammation could potentially be biomarkers for assessing GO activity and predicting the course of GO after RAIT.

Aim: The purpose of this study was to evaluate the dynamics of eye symptoms and analyze immunological parameters: cytokine TGF-β1 and cytokine receptors: sTNFα-R1, sTNFα-R2, sIL-2R, sIL-6R over time after RAIT, as possible predictors of GO activation.

Materials and methods: The study included 59 patients (118 orbits) with GD in the state of euthyroidism and subclinical hyperthyroidism and low active and inactive GO, aimed at conducting RAIT. Concentrations of cytokine TGF-β1, sTNFα-RI and sTNFα-R2, sIL-2R, sIL-6R, TSH receptor antibodies (rTSH-Ab), free thyroxine (FT4) and free triiodothyronine (FT3), -thyroid-stimulating hormone (TSH) in the blood serum were determined. Ultrasound examination of the thyroid gland, multispiral computed tomography (MSCT)/magnetic resonance imaging (MRI) of the orbits was performed. The examination was carried out 3, 6, 12 months after the RAIT.

Results: The deterioration of the course of the GO (1-2 points according to CAS) was noted after 3 months. (32.5%) and to a lesser degree after 6 and 12 months (13.2% and 8.45%, respectively). Dynamics were not noted, approximately, in the same number of patients (40.5%, 41.5%, 45.8%, respectively). An improvement in the course of the GO was noted after 6 and 12 months (45.3, 45.8, respectively). After 3 and 6 months, the achievement of hypothyroidism and a significant increase in the level of rTSH-Ab were noted. In the analysis of cytokines and their receptors a significant decrease in the level of TGF-β1 was noted after 3, 6 and 12 months. There was also a significant decrease in sTNF-R1 and sIL-2R at 3 and 6 months. The level of sTNFα-R2 significantly decreased 3 months after RAIT. The level of sIL-6R has not changed significantly. After 3 months in patients with positive dynamics of image intensification, the level of TGF-β1 did not significantly change compared with the level before RAIT, in patients with worsening of the course of GO or without dynamics, the level of TGF-β1 significantly decreased. After 6 months, there was the same trend, not reaching statistical significance. The IgG4 level and the IgG4/IgG ratio increased to 6 and 12 months, which corresponded to an increase in diplopia index.

Conclusion: The main limiting factor in the conduct of RAIT is the activity of the autoimmune process in the orbits. Since patients with inactive (CAS 0-2) or low activity (CAS 3-4) GO were referred for RAIT, there was no pronounced activation of GO after RAIT. There was a slight deterioration in the course of GO by only 1-2 points according to CAS after 3 months. (32.5%) and to a lesser degree after 6 months (13.2%). In the study, it was found that the main predictors of the deterioration of the course of GO after RAIT are uncompensated hypothyroidism, a high level of rTSH-Ab and a decrease in the level of cytokine TGF-β1.