Review Question - QID 210517

A 14-year-old girl is brought to the pediatrician by her mother. The girl's mother states that she began having her period 6 months ago. After her first period, she has had a period every 10 to 40 days. Her menses have ranged from very light flow to intense and severe symptoms. Otherwise, the patient is doing well in school, is on the track team, and has a new boyfriend. Her temperature is 98.1°F (36.7°C), blood pressure is 97/58 mmHg, pulse is 90/min, respirations are 14/min, and oxygen saturation is 99% on room air. Physical exam demonstrates an obese girl but is otherwise within normal limits. Which of the following is the most likely diagnosis?