Background: Graves disease (GD) is the most common cause of hyperthyroidism in the pediatric population. T helper 17 (Th17) IL-17A+CD3+CD4+ cells represent a novel subset of T helper cells that play an active role in inflammatory and autoimmune diseases. Although methimazole (MMI) lowers the levels of thyroid autoantibodies, little is still known about its influence on cell-mediated immune response. The role of Th17 cells in GD pathogenesis remains uncertain and the impact of MMI treatment on these cell subset has not been investigated.
Aims and objectives: The aim of this research was to describe the percentages and absolute counts of Th17 lymphocytes in children with GD and to assess changes in the amount of these cell subset during MMI treatment. The relationships between Th17 and selected clinical parameters were also assessed.
Methods: The frequencies of Th17 cells were measured by flow cytometry in 60 adolescents at the time of GD diagnosis and after achieving MMI-induced euthyreosis. The control group consisted of 20 healthy volunteers.
Results: Higher absolute counts of Th17 lymphocytes were found in hyperthyroid adolescents before the treatment initiation and after achieving euthyreosis than in healthy individuals (P=0.0001 and P=0.047). Treatment with MMI caused a significant decrease in the percentages and absolute counts of Th17 lymphocytes (P=0.047 and P=0.043). Before the treatment, the serum concentration of TSH correlated inversely with the absolute counts and percentages of Th17 cells (absolute count: r=−0.3514, P=0.001; percentage: r=−0.3731, P=0.001).
Conclusions: Despite the observed high frequencies of Th17 cells in GD adolescents in comparison with controls, and its tendency to decrease after MMI administration, treatment with MMI did not lead to the normalization of Th17 levels. Obtained results suggest also that severe immune system deregulation in the form of extremely high numbers of Th17 cells may lead to rapid GD relapse after the treatment.