Objective: The high incidence of non-organ specific autoantibodies in patients with mitral valve prolapse (MVP) may suggest an association between MVP and autoimmune diseases. A higher incidence of MVP in patients with chronic lymphocytic thyroiditis and Graves' disease has been demonstrated in various studies. In particular, an increased incidence of MVP in patients with autoimmune thyroid disease characterized with hyperthyroidism may suggest an association between MVP and thyroid functions. To the best of our knowledge, there is a lack of literature regarding the evaluation of autoimmune thyroid diseases in patients with MVP. This study primarily aimed to evaluate the autoimmune thyroid disease using thyroid ultrasonography and autoimmune thyroid antibodies in patients with MVP.