A thirty-five-year-old woman with recently diagnosed hyperth…
A thirty-five-year-old woman with recently diagnosed hyperthyroidism presents with weight loss, heat intolerance, tremor, and palpitations. Earlier this week, laboratory tests showed suppressed thyroid-stimulating hormone and elevated free thyroxine. Today her heart rate is one hundred twenty beats per minute and irregularly irregular. She is anxious and diaphoretic. What is the most urgent first step?