Endocrine Abstracts

Background: Increased production of reactive oxygen species (ROS) and oxidative stress play a significant role in the initiation and persistence of the autoimmune process in Graves’ disease (GD)

Aim: To study the ROS level of peripheral blood monocytes in patients with GD after radioactive iodine (RAI).

Materials and Methods: The study included 48 patients with a confirmed diagnosis of GD, from 18 to 65 years (mean 46.42 ± 15.26 years). The hormonal status and functional activity of blood monocytes in patients were studied on the day of RAI and 1, 3 and 6 months after RAI. To measure ROS, spontaneous luminol- and lucigenin-dependent luminescence, luminescence induced by zymosan, were determined using the chemiluminescence method with a BLM-3607 analyzer (MedBioTeh, Krasnoyarsk). The rate of reaction development, the maximum level of ROS, the total ROS were determined.

Results: Before RAI the thyroid status of patients corresponds to subclinical thyrotoxicosis that developed when thyrostatic therapy was canceled: TSH 0.08 mU/l (0.01; 0.45), free T4 17.49 pmol/l (12.88; 21.44), free T3 5.28 pmol/l (4.32; 7.38), 12.80 IU/l (5.77; 26.58). Monitoring of patients reveals normalization of TSH levels, a decrease in free fractions of thyroid hormones. The level of TRAb decreased 6 month after RAI – 1.48 IU/l (0.86; 2.91). A decrease in all parameters of lucigenin-dependent spontaneous chemiluminescence in patients with GD compared to the control was revealed: the time to maximum (Tmax) (P< 0,001), the maximum luminescence level (Imax) (P=0,038) and the total ROS (S) were reduced (P=0,011). Differences were determined for all points of observation. There were no statistically differences between the control and patients with GD before RAI in the parameters of luminol-dependent chemiluminescence of monocytes. After RAI decrease in parameters was found when comparing the controls and patients 1, 3 and 6 months after therapy: in luminol-dependent spontaneous chemiluminescence S was reduced (P=0,009, P=0,018, P=0,033, resp.), in chemiluminescence of the induced by zymosan, Imax (P=0,005, P=0,022, P=0,019 resp.) and S were reduced (P=0,008, P=0,017, P=0,019 resp.).

Conclusion: Decrease in the level of initial and induced primary ROS and the total ROS production in blood monocytes of patients with GD before RAI, compared to the control was revealed, that may be a sign of immunomodulatory and restrictive effects of thiamazole, despite the development of subclinical hyperthyroidism. After RAI, the level of primary and secondary ROS of monocytes decreases, that indicates the immunosuppressive effect of RAI and inhibition of autoimmune process.