- Objective Platelets can modulate lymphocytes’ role in the pathophysiology of thyroid autoimmune diseases. The present study was performed to clarify the status of platelet-lymphocyte subpopulations aggregation in circulating blood in patients with Graves’ disease (GD). Methods One hundred and fifty patients with GD (GD group) and 45 hyperthyroid patients with toxic multinodular goiter (TMG group) were recruited in the study. Control group consisted 150 healthy subjects. Immunophenotyping of lymphocytes was performed by flow cytometry. Detection of lymphocyte-platelet aggregates (LPAs) was done using light microscope after Ficoll-gradient centrifugation. Results The group of GD patients exhibited reduced CD8 lymphocyte and higher CD19 cell counts compared with TMG group and healthy controls. A greater number of activated CD3 +, HLA-DR + lymphocytes were observed in GD than in TMG group and control group. GD group was characterized by lower blood platelet count (232 ± 89 × 103 cells/μL) than TMG group (251 ± 97 × 103 cells/μL; P < 0.05) and control group (262 ± 95 × 103 cells/μL; P < 0.05). In GD group, more platelet-bound lymphocytes (332 ± 91 /μL) were found than that in TMG group (116 ± 67/μL, P < 0.005) and control group (104 ± 58 /μL; P < 0.001). Conclusions GD is associated with higher levels of activated lymphocytes and lymphocyte-platelet aggregates.