FACTITIOUS HYPERTHYROIDISM CAUSING ACUTE MYOCARDIAL-INFARCTION

Myocardial ischemia is a rare but severe and possibly life threatening manifestation of hyperthyroidism, but does not usually result in pers istent ischemia, We report on a 71-year-old woman who had undergone to tal thyroidectomy with subsequent irradiation because of follicular ca rcinoma 3 years ago, Since then, she had been maintained on oral levot hyroxine replacement therapy at a dose of 0.15 mg alternating with 0.2 mg daily, When latent hypothyroidism became evident despite replaceme nt therapy, the dose of levothyroxine was increased to 0.3 mg a day, T hree weeks later, the patient suffered from an acute posterior myocard ial infarction, although she had no previous history of coronary arter y disease. Subsequent coronary arteriograms revealed no evidence of di sease of the major vessels, Myocardial scintigraphy 3 weeks after infa rction still revealed a persistent perfusion defect, Since it is known that thyroid hormones increase oxygen demand, the rapid elevation of oxygen utilization caused by thyrotoxicosis factitia is likely to be r esponsible for this patient's myocardial infarction, The case illustra tes that a sudden increase in levothyroxine replacement dose should be avoided.