We would like to present here our experience with a 37-year-old male patient who was admitted to our department because of chest pain. Laboratory findings and ST-segment elevation on his ECG were indicative of acute myocardial infarction. He had no coronary artery disease history, he did not use drugs or alcohol, and, except for a history of moderate smoking, he had no other risk factors for coronary artery disease. A history of subtotal thyroidectomy 17 years before hospital admission was reported. Since then, he had not undergone any medical follow-up, as he had been totally asymptomatic. A suspicion of a metabolic disorder was confirmed because of QT-interval prolongation on the ECG and a clinical examination finding that was positive for Trousseau sign. Laboratory analysis revealed severe hypocalcemia (Ca2+ level, 5.86 mg/dL; normal range, 8.2 to 10.7 mg/dL), hyperphosphatemia (phosphate level, 6.06 mg/dL; normal range, 2.4 to 4.9 mg/dL), and low serum levels of parathyroid hormone (parathyroid hormone level, 5 pg/mL; normal range, 10 to 55 pg/mL), while thyroid-function tests revealed hyperthyroidism (human thyroid-stimulating hormone level, 0.005 IU/mL; normal range, 0.27 to 4.2 IU/mL; and free 3,5,3′-triiodothyronine level, 7 pg/mL; normal range, 1.82 to 4.62 pg/mL).