Peripheral blood lymphocyte apoptosis and its relationship with thyroid function tests in adolescents with hyperthyroidism due to Graves' disease

INTRODUCTION Failures in apoptotic pathways can contribute to various autoimmune diseases, including autoimmune hyperthyroidism due to Graves' disease (GD). The aim of the present research was to assess changes in the degree of peripheral blood (PB) lymphocyte apoptosis during methimazole (MMI) treatment in the group of teenage children, and to describe its relationship with thyroid function tests. MATERIAL AND METHODS The percentage of PB apoptotic lymphocytes, assessed by the decrease in mitochondrial transmembrane potential (CMXRos staining), was measured in 30 adolescents at the time of diagnosis and after obtaining normalization of the thyroid hormone levels. RESULTS The percentage of apoptotic lymphocytes in previously untreated patients with GD (5.16 ±2.81%) was significantly lower (p = 0.000001) than the percentage of apoptotic cells in the same group of patients after obtaining methimazole-induced euthyroidism (10.72 ±4.66%). There was a correlation between the increase of the mean percentages of apoptotic lymphocytes and the reduction of FT4 levels (R = 0.63, p < 0.0001), as well as the reduction of TT3 levels (R = 0.95, p < 0.0001). The more signs and symptoms accompanying the diagnosis of GD, the higher was the increment of the degree of lymphocyte apoptosis observed during the MMI-treatment (R = 0.74, p < 0.0000001). The methimazole dosage correlated (R = 0.85, p < 0.0001) with the percentage of apoptotic cells. CONCLUSIONS The use of methimazole in treatment of hyperthyroidism due to GD leads to an increment of apoptotic cells in PB. Higher doses of methimazole cause a higher increase of apoptotic lymphocytes. Apoptosis induction of human PB lymphocytes seems to be one of the indicators of proper hyperthyroidism treatment.