A 17-year-old female was referred to the endocrinology clinic after blood test results suggestive of hyperthyroidism. She had mild symptoms of thyrotoxicosis, including menstrual disturbance with intermittent palpitations and tremor. On examination, the patient was normotensive, tachycardic (100 beats/min), and of slim build with poor dentition. She had a small diffuse goiter without retrosternal extension or bruit. There was conjunctival injection but no evidence of lid lag or proptosis. Auscultation of the precordium revealed murmurs in systole and diastole consistent with mixed aortic valve disease.