Anorexia Nervosa

A 16-year-old was brought to a pediatrician's office by her parents for evaluation. She was visiting the doctor reluctantly and said that she had no health concerns. However, her parents reported that for 5 months she had been eating a highly restrictive diet consisting mainly of vegetables and small amounts of chicken or turkey, had declined to increase her food intake, and was progressively losing weight. On examination, her body-mass index (BMI, the weight in kilograms divided by the square of the height in meters) was 17.5 (weight, 108 lb [49 kg], and height, 5 ft 7 in. [170 cm]). Her blood pressure while sitting was 100/78 mm Hg, which decreased to 78/60 mm Hg after she stood for 3 minutes. Her resting pulse was 46 beats per minute. Her skin was dry, and her hair was thinning at her scalp. An examination of her oral cavity revealed extensive erosion of the dental enamel. How would you further evaluate and treat this patient?