A 49-year-old woman presents with palpitations, tremors, excessive sweating, fatigability, and insomnia for two months. She lost five kilograms of weight during this time. She did not seek medical attention for her symptoms. She was diagnosed with type 2 diabetes mellitus three years ago. This is well controlled on diet, exercise, and oral metformin 850 mg daily. She has no microvascular or microvascular complications. She is not on any other medications. Her surgical and gynecological histories are unremarkable. Her menopause took place two years ago. She is a professional (and popular) singer. Her random plasma glucose is 134 mg/dL (normal: <180 mg/dL). Serum electrolytes and a renal profile are within normal parameters. A 12-lead ECG reveals sinus tachycardia.