In the presence of angina pectoris in a premenopausal woman without significant risk factors for coronary disease, we have to rule out other causes of coronary lesion of non atherosclerotic origin. The relations between hyperthyroidism and the cardiovascular system are well known, but hyperthyroidism is responsable for less than 5% of all causes of chest pain. We present a clinical case of a 47 year old woman with typical chest pain and eletrocardiogram (EKG) suggesting coronary ischemia but with normal laboratory data. Anamnesis, clinical and the laboratory data confirmed the diagnosis of hyperthyroidism. Further investigation showed a normal coronary angiography. After treatment with radioiodine and the establishment of euthyroidism, the patient remained asymptomatic and EKG and myocardial scintilography were negative for ischemia. These results suggest a cause and effect relationship between thyroid overactivity and myocardial ischemia, implying a probable etiological role for hyperthyroidism in the clinical and EKG findings.