eng Science and Education Publishing American Journal of Medical Case Reports 2374-216X 2021-01-14 9 3 194 197 10.12691/ajmcr-9-3-15 AJMCR20219315 article Andrew V. Doodnauth 1 Fadi Yacoub 1 Vaibhavi Solanki 1 Andrea Trimmingham 1 Lina Soni 1 Samy I. McFarlane Smcfarlane@downstte.edu 1 Department of Internal Medicine, State University of New York: Downstate Medical Center, Brooklyn, New York, United States- 11203 Thyroid hormone has a major role in cardiovascular function and cardiac hemodynamics. A slight change in thyroid affects ventricular function, serum cholesterol levels, increases the risk of coronary artery disease as well as cardiovascular mortality. In this report, we present a 62-year-old female with history significant for ischemic heart disease who was admitted for acute coronary syndrome (ACS) with persistent tachycardia, requiring urgent cardiac catheterization. Complete cardiac workup revealed that the patient had most likely suffered from vasospastic angina secondary to inadvertent overdose of her prescribed levothyroxine. This report emphasizes the significant cardiac complications caused by a deluged hyperadrenergic state secondary to overt hyperthyroidism. We conclude that thyrotoxicosis is a significant risk factor for cardiovascular disease and should be considered as a cause of life-threatening myocardial ischemia, especially in patients with known ischemic heart disease and thyroid disorders. http://pubs.sciepub.com/ajmcr/9/3/15/ajmcr-9-3-15.pdf thyroid hormone ischemic heart disease acute coronary syndrome levothyroxine hyperthyroidism cardiovascular disease