Review Question - QID 214950

A 17-year-old girl is brought to the primary care clinic by her parents for increasing fatigue over the past week. The patient says that she just feels tired because she has been working out more lately. She denies limiting her food intake, saying that she overeats if anything. She denies sensitivity to temperature changes and has regular menstrual cycles. She has no past medical history and does not take any medications. She is a competitive gymnast. Her temperature is 98.6°F (37.0°C), blood pressure is 108/74 mmHg, pulse is 48/min, respirations are 16/min, and her body mass index (BMI) is 17.0 kg/m2. Physical exam reveals a thin girl with a flat affect, several dental cavities, dorsal calluses on her knuckles, and soft, downy hair on her arms. What is the most likely diagnosis?