Kaplan USMLE Step 2: No menstrual period for nearly two years

If you’re preparing for the United States Medical Licensing Examination® (USMLE®) Step 2 exam, you might want to know which questions are most often missed by test-prep takers. Check out this example from Kaplan Medical, and read an expert explanation of the answer. Also check out all posts in this series.

A 29-year-old woman comes to the physician because she has not had a menstrual period in nearly two years. Menarche was at age 12, and prior to her pregnancy, menses occurred every 30 days and consisted of three days of light bleeding. The patient had a vaginal delivery 11 months ago, which was complicated by hemorrhage due to retained placental tissue that required treatment with a suction curettage and multiple transfusions. The patient stopped breastfeeding five months ago when she stopped producing milk. Medical history is unremarkable, and she takes no medications. Her temperature is 36.6ºC (97.9ºF), pulse is 76/min, respirations are 12/min, and blood pressure is 118/76 mm Hg. A pelvic examination is within normal limits. Prolactin, thyroid-stimulating hormone (TSH), and follicle-stimulating hormone (FSH) levels are within normal limits. The patient is prescribed 10 mg of medroxyprogesterone daily for 10 days, after which she does not have any vaginal bleeding. Which of the following is the most likely cause of this patient's presentation?

A. Intrauterine scarring

B. Lactational amenorrhea

C. Mullerian anomaly

D. Pituitary adenoma

E. Pituitary infarction

The correct answer is A.

The single best answer is intrauterine scarring because it can cause secondary amenorrhea subsequent to uterine suction curettage and is characterized by no withdrawal bleeding during a progestin withdrawal test and normal levels of prolactin, TSH, and FSH.

Choice B. Lactational amenorrhea refers to amenorrhea which occurs for three-six months postpartum in patients who are currently exclusively breastfeeding.