Understanding Irregular Periods: Causes, When to Worry

Irregular menstrual cycles are common, especially during adolescence and perimenopause. However, persistent irregularity may signal underlying pathology.

Defining Irregular

• Cycle length <21 or >35 days
• Cycle-to-cycle variation >7–9 days
• Absent periods (amenorrhea): >90 days (non-pregnant)
• Unpredictable bleeding pattern

Common Causes by Life Stage

Adolescence (Menarche–2–3 yrs)

Immature HPO axis → anovulatory cycles. Usually self-resolves.

Reproductive Years

• PCOS: #1 cause (oligo/anovulation, hyperandrogenism, polycystic ovaries).
• Thyroid dysfunction: Hypo- or hyperthyroidism.
• Hyperprolactinemia: Prolactinoma, medications.
• Weight extremes: Low BMI (hypothalamic amenorrhea), obesity (insulin resistance).
• Excessive exercise/stress: Functional hypothalamic amenorrhea.
• Contraceptives: Hormonal IUD, implant, pills (withdrawal bleeds ≠ true periods).
• Perimenopause (40s–50s): Declining ovarian reserve → erratic cycles.

Structural/Pathologic

• Uterine fibroids, polyps, adenomyosis
• Endometrial hyperplasia/cancer (postmenopausal bleeding = cancer until proven otherwise)
• Coagulopathies (von Willebrand)

When to See a Clinician

• Irregularity persists >6 months (adults) or >3 years post-menarche
• Cycles <21 or >45 days consistently
• Heavy bleeding (soaking pad/tampon q1–2h, clots >1", >7 days)
• Bleeding between periods or after sex
• Severe pain (dysmenorrhea)
• Trying to conceive >12 mos (<35) / 6 mos (≥35)
• Signs of hyperandrogenism (hirsutism, acne, hair loss)
• Postmenopausal bleeding

Basic Workup

Pregnancy test, TSH, prolactin, FSH/LH/estradiol (day 3), androgens, pelvic ultrasound. Further per findings.

Track cycles (app/calendar) to provide accurate history. Most causes are treatable.