FCOG-1047

FCOG-1047

A 23-year-old female came to see you because of absent menses for the last 5 months. She reports that in the past, menstrual periods were regular, every 28 days. Her first menstrual periods were at the age of 12. She is sexually active with her boyfriend and they use condoms consistently. She does not use oral contraceptive pills. She eats a healthy diet and does not smoke or drink alcohol.
Physical examination is non-remarkable. Pregnancy test is negative. Which of the following is the most appropriate next step in the evaluation of this patient?