Increased concentration of T‐cell receptor rearrangement excision circles (TREC) in peripheral blood in Graves' disease

Summary Background T‐cell receptor rearrangement excision circles ( TREC ) are circular DNA molecules generated during T‐cell maturation in the thymus. Recent studies suggested that a decreased TREC concentration in peripheral blood may be a general feature of autoimmunity. Our purpose was to assess the TREC concentration in Graves' disease ( GD ). Methods TREC concentration was assessed by real time PCR in DNA samples isolated from peripheral blood leucocytes among younger ( n = 94, age range 6–29 years) and older patients with GD ( n = 93, age range 57–80 years) and age‐matched controls ( n = 206). Results TREC concentration decreased with age in all subjects, but it was significantly higher in GD compared with controls ( P = 9·4 × 10 −10 ). TREC concentration was higher ( P = 0·0038) in hyperthyroid ( n = 78) than euthyroid ( n = 82) patients with GD , but in both groups, it remained increased relative to controls ( P = 2·2 × 10 −11 and P = 4·4 ×10 −7 , respectively). Conclusions Patients with GD , particularly those with hyperthyroidism, have increased concentration of TREC which may suggest increased rather than decreased thymic activity. Thus, GD does not follow the paradigm suggested for other autoimmune disorders which links autoimmunity with thymic senescence.