A 42-year-old woman presents to your primary care office with complaints of irregular menses over the last 8 months and her last menstrual period was two months ago. She is particularly distressed due to irregular, unpredictable episodes of increased skin temperature and sweating lasting about 3 to 4 minutes at a time. These sudden feelings of sweating disrupt her sleep and impact her day-time productivity at home and work. Review of systems is remarkable for irritability, mood swings, vaginal dryness, discomfort during intercourse, decreased sex drive, and increased urinary frequency. She is sexually active and still has the uterus. Her vital signs and physical examination are normal. As you analyze her symptoms, you wanted to run some tests that indicate decreased ovarian reserve. Which of the following is the earliest marker to indicate decreased ovarian reserve?
