Secondary Amenorrhea in a Woman with Late Menarche
The most likely diagnosis is Polycystic Ovary Syndrome (PCOS), which is one of the four most common causes of secondary amenorrhea in reproductive-aged women. 1, 2
Why PCOS is the Most Likely Answer
PCOS is the most common endocrinopathy among reproductive-aged women, affecting approximately 5-10% of this population, and represents one of the four primary causes of secondary amenorrhea. 1, 2, 3, 4
Key Supporting Evidence:
- PCOS accounts for the majority of secondary amenorrhea cases when considering the four main etiologies (PCOS, functional hypothalamic amenorrhea, hyperprolactinemia, and primary ovarian insufficiency). 1, 2
- Late menarche (age 15) is associated with menstrual disorders and increased risk of PCOS, as both early and late menarche correlate with higher rates of menstrual irregularities. 5
- PCOS characteristically presents with oligomenorrhea or amenorrhea as one of its cardinal features, along with hyperandrogenism and polycystic ovarian morphology. 3, 4
Why "Ovulation Dysgenesis" is Not the Answer
"Ovulation dysgenesis" is not a recognized medical diagnosis. The term appears to be a distractor or possibly a mistranslation. The correct term would be "ovarian dysgenesis," which refers to conditions like Turner syndrome that cause primary amenorrhea (never having menstruation), not secondary amenorrhea. 6, 7
Critical Distinction:
- This patient had menarche at age 15, meaning she established menstrual cycles, which rules out primary ovarian failure conditions like ovarian dysgenesis. 6
- Primary ovarian insufficiency (POI) would present with elevated FSH and LH levels and typically occurs later in life or after established regular cycles. 1, 7
Diagnostic Approach for This Patient
The initial evaluation must include a pregnancy test first, followed by measurement of FSH, LH, prolactin, and TSH levels. 1, 2, 8
Laboratory Findings Expected in PCOS:
- LH:FSH ratio >2 suggests PCOS. 1, 9
- Normal or mildly elevated androgens (testosterone >2.5 nmol/L). 5
- Pelvic ultrasound showing polycystic ovarian morphology (≥12 follicles of 2-9mm per ovary). 5, 1
Important Diagnostic Pitfall:
Do not confuse PCOS with FHA-PCOM (functional hypothalamic amenorrhea with polycystic ovarian morphology), which affects 40-47% of women with FHA and can fulfill Rotterdam criteria for PCOS but requires completely different treatment. 1, 9, 2 FHA-PCOM is distinguished by:
- History of energy deficit, excessive exercise, or stress 1, 9
- Negative progestin challenge test (indicating low estrogen) 1, 2
- Lower LH levels and higher SHBG compared to true PCOS 1, 9
Clinical Implications
Patients with PCOS require screening for metabolic complications, as they are four times more likely to develop type 2 diabetes mellitus and have twice the prevalence of metabolic syndrome compared to the general population. 3, 6
Treatment depends on the patient's primary concerns: