Background: Patients suffering from Graves disease (GD) exhibit thyroid enlargement on account of excessive activation and proliferation of thyroid epithelial cells.Precise molecules involved and the underlying mechanism has not been fully elucidated.Signal transducer and activator of transcription 6 (STAT6) has a crucial impact in the regulation of proliferation, however, little is known about the STAT6 phosphorylation status in the GD patients, as is the role of STAT6 on thyroid epithelium.