TPO and pericardial effusion: Echocardiography is then performed to confirm pericardial effusion and assess for tamponade physiology. If there are clinical or historical clues suggestive of hyperthyroidism (as in our case), thyroid function tests (TSH, free T4, ± free T3) and autoantibody assays (TRAb, anti-TPO) help determine whether Graves' disease is the underlying cause.