Reproductive · Year 2 · from Reproductive
Case 3: Ovulation Induction with Letrozole
Clinical Image
Source: Wikipedia - Folliculogenesis - CC BY-SA 4.0
Case Presentation
A 29-year-old woman with PCOS presents for infertility evaluation. She and her husband have been attempting pregnancy for 14 months. Her menstrual cycles occur every 45-90 days. She has mild hirsutism (Ferriman-Gallwey score 10) and BMI 31. Laboratory studies show LH 14 mIU/mL, FSH 5 mIU/mL (LH:FSH ratio 2.8:1), total testosterone mildly elevated, and normal TSH and prolactin. Her husband's semen analysis is normal. Transvaginal ultrasound shows bilateral polycystic ovarian morphology with multiple peripheral follicles and ovarian volume of 12 mL bilaterally. HSG demonstrates bilateral tubal patency. The diagnosis is anovulatory infertility secondary to PCOS. After counseling about weight loss (she loses 8 lbs over 2 months with modest improvement in cycle regularity), ovulation induction with letrozole is initiated. She receives letrozole 5 mg daily on cycle days 3-7. Transvaginal ultrasound on cycle day 12 shows a 19 mm dominant follicle. She receives hCG trigger injection and has timed intercourse. Mid-luteal progesterone is 14 ng/mL, confirming ovulation. She conceives on the second treatment cycle.
Key Learning Points
- PCOS is characterized by anovulation, hyperandrogenism, and polycystic ovarian morphology; it is the most common cause of anovulatory infertility
- Letrozole (aromatase inhibitor) is first-line for ovulation induction in PCOS, with higher live birth rates than clomiphene in randomized trials
- Follicular monitoring with ultrasound ensures appropriate response and timing; hCG trigger induces final oocyte maturation and ovulation
- Mid-luteal progesterone >3 ng/mL confirms ovulation; levels >10 ng/mL suggest adequate luteal function