USMLE (United States Medical Licensing Examination): Step 1: Basic sciences assessment Practice Exam 12
Practice exam for USMLE (United States Medical Licensing Examination): Step 1: Basic sciences assessment.
Question 1
MEDIUMA 28-year-old woman presents to her physician with infertility for 18 months. She reports irregular menstrual cycles occurring every 45–70 days since menarche. She has gained 10 kg (22 lb) over the past 2 years and notes increased facial hair growth. She takes no medications. Temperature is 36.8°C (98.2°F), blood pressure is 124/78 mm Hg, pulse is 76/min, and BMI is 33 kg/m². Physical examination shows acne and hirsutism. Laboratory studies show elevated total testosterone and an increased LH:FSH ratio. Which of the following best explains the mechanism leading to this patient’s anovulation?
This presentation is consistent with polycystic ovary syndrome (PCOS): oligomenorrhea, hyperandrogenism, obesity, and elevated LH:FSH ratio. Insulin resistance leads to hyperinsulinemia, which stimulates theca cells to produce androgens and decreases hepatic SHBG, increasing free androgens; this impairs follicular maturation and ovulation. Prolactin-mediated GnRH suppression would suggest hyperprolactinemia (galactorrhea, headaches/visual changes). Premature ovarian insufficiency causes high FSH with low estrogen and typically amenorrhea rather than long, irregular cycles.
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