# Clinical Cases: Menstrual Cycle and Ovulation

## Case 1: Anovulatory Bleeding (Dysfunctional Uterine Bleeding)

### Clinical Image
![Anovulatory Cycle](case_01_image.jpg)
*Source: [Wikipedia - Menstrual cycle](https://en.wikipedia.org/wiki/Menstrual_cycle) - CC BY-SA 4.0*

### Case Presentation
A 17-year-old female presents with irregular, heavy menstrual bleeding for the past year. Since menarche at age 12, her periods have been unpredictable, occurring anywhere from every 2 weeks to every 3 months. When she does bleed, it is often heavy (soaking through a pad every 1-2 hours for 3-4 days) and prolonged (lasting 10-14 days). She denies sexual activity, hirsutism, or galactorrhea. Physical examination reveals a healthy-appearing adolescent with BMI 24. There is no hirsutism, acne, or acanthosis nigricans. Pelvic examination is deferred given her age and lack of sexual activity. Laboratory studies show hemoglobin 10.2 g/dL (mild anemia), TSH normal, prolactin normal, and pregnancy test negative. Given her age and body habitus, PCOS workup is low yield at this time. Transvaginal ultrasound is not performed given her virginal status. The diagnosis is anovulatory uterine bleeding, common in adolescents due to hypothalamic-pituitary-ovarian axis immaturity. Treatment is initiated with combined oral contraceptives to regulate her cycles and reduce bleeding. Iron supplementation is prescribed for her anemia. She is counseled that many adolescents develop regular ovulatory cycles within a few years of menarche, but if symptoms persist, evaluation for PCOS would be warranted.

### Key Learning Points
- Anovulatory cycles are common in the first 2-3 years after menarche due to HPO axis immaturity; without ovulation, no corpus luteum forms, and no progesterone is produced
- Unopposed estrogen stimulates endometrial proliferation; when estrogen levels fluctuate, the endometrium sheds unpredictably, causing irregular and often heavy bleeding
- Combined oral contraceptives provide cycle control by suppressing the HPO axis and providing regular hormone withdrawal bleeding
- If anovulation persists beyond adolescence, PCOS should be considered as the most common cause in reproductive-age women

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## Case 2: Luteal Phase Defect

### Clinical Image
![Luteal Phase](case_02_image.jpg)
*Source: [Wikipedia - Corpus luteum](https://en.wikipedia.org/wiki/Corpus_luteum) - CC BY-SA 3.0*

### Case Presentation
A 34-year-old woman presents for evaluation after two first-trimester miscarriages in the past 18 months. She and her husband have been trying to conceive for 2 years. Her menstrual cycles are regular at 24-25 days. She reports consistent premenstrual spotting for 3-4 days before the onset of her full menstrual flow. She uses ovulation predictor kits and typically gets a positive test on day 11 or 12. Basal body temperature charting shows a biphasic pattern with the luteal phase lasting only 9-10 days before temperature drops and menses begins. Physical examination is unremarkable. Day 21 (mid-luteal) progesterone level is 6.2 ng/mL (low-normal). Given her short luteal phase, low mid-luteal progesterone, and premenstrual spotting, a diagnosis of luteal phase defect is considered. She undergoes hysterosalpingogram which shows normal tubal patency. Her husband's semen analysis is normal. The patient conceives on a subsequent cycle but given her history, progesterone supplementation (vaginal progesterone 200 mg twice daily) is initiated after positive pregnancy test and continued through 10 weeks of gestation. She carries the pregnancy to term without complications.

### Key Learning Points
- The luteal phase is typically 14 days (+/- 2 days); a short luteal phase (<10 days) may indicate inadequate corpus luteum function
- Progesterone from the corpus luteum is essential for secretory transformation of the endometrium, creating an environment suitable for implantation
- Luteal phase defect may present with premenstrual spotting, short luteal phase, and recurrent early pregnancy loss
- Progesterone supplementation is commonly used in early pregnancy for women with history of recurrent loss, though evidence for efficacy outside of IVF is debated

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## Case 3: Ovulation Induction with Letrozole

### Clinical Image
![Follicular Monitoring](case_03_image.jpg)
*Source: [Wikipedia - Folliculogenesis](https://en.wikipedia.org/wiki/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