Prolonged Menstrual Cycles (Oligomenorrhea): Causes, Evaluation, and Management

Defining Prolonged Cycles

• Oligomenorrhea: Cycles >35 days (or <9 periods/year).
• Amenorrhea: No period for ≥3 consecutive cycles (or 6 months).

Common Etiologies

1. Hormonal Imbalance: Estrogen/progesterone dysregulation (adolescence, perimenopause).
2. PCOS: Hyperandrogenism, anovulation, polycystic ovaries – #1 cause in reproductive age.
3. Thyroid Dysfunction: Hypothyroidism (↑TRH → ↑Prolactin → suppresses GnRH); hyperthyroidism also disrupts cycles.
4. Weight/Energy Imbalance: Low BMI, rapid weight loss, excessive exercise → hypothalamic amenorrhea.
5. Medications/Contraceptives: OCPs, depot progestins, antipsychotics, chemotherapy; transition on/off can cause temporary irregularity.
6. Stress: Chronic stress → HPA axis activation → suppresses HPG axis.
7. Pregnancy: Always rule out first.
8. Perimenopause: Declining ovarian reserve → irregular, then absent cycles.
9. Structural/Pathologic: Uterine fibroids, adenomyosis, PID, Asherman's syndrome, ovarian/uterine cancer (rare).
10. Circadian Disruption: Shift work, jet lag affect hormonal rhythms.

When to Seek Evaluation

• Cycles consistently >35 days.
• <3 cycles in 6 months.
• Associated symptoms (hirsutism, acne, weight change, galactorrhea, pelvic pain).
• Trying to conceive >12 months (or >6 months if >35).

Diagnostic Approach

• History, physical, BMI.
• Labs: β-hCG, TSH, prolactin, FSH/LH (day 3), estradiol, androgens, HbA1c.
• Pelvic ultrasound (ovarian morphology, endometrial thickness).

Management

Target underlying cause: lifestyle modification (weight, stress), thyroid treatment, insulin sensitizers (PCOS), cyclic progestins (endometrial protection), fertility agents if desired. Combined OCPs regulate cycles but don't "fix" etiology.