What is the initial workup for a patient presenting with irregular menstrual periods?

Initial Workup for Irregular Menstrual Periods

The initial workup for irregular menstrual periods should include a thorough menstrual history, physical examination, laboratory testing (FSH, LH, estradiol, prolactin, TSH, and pregnancy test), and transvaginal ultrasound to evaluate for structural causes. 1

Comprehensive History Assessment

• Obtain detailed menstrual history:

  • Age of menarche
  • Regularity of menses (cycle length <21 or >35 days indicates irregularity)
  • Duration and amount of bleeding
  • Presence of intermenstrual bleeding
  • Use of medications that could affect menstruation
  • Other health issues
  • Family menstrual history 2

• Assess for symptoms suggesting specific etiologies:

  • Galactorrhea (suggesting hyperprolactinemia) 3
  • Hirsutism, acne, weight gain (suggesting PCOS)
  • Hot flashes, night sweats (suggesting premature ovarian insufficiency)
  • Dysmenorrhea, dyspareunia (suggesting endometrial or structural abnormalities)

Physical Examination

• Vital signs including BMI
• Assessment of secondary sex characteristics and pubertal stage
• Signs of hyperandrogenism (hirsutism, acne)
• Signs of eating disorders or significant weight changes
• Thyroid examination
• Breast examination for galactorrhea
• Pelvic examination to assess for pregnancy, vaginal atrophy, or structural abnormalities 2

Laboratory Testing

• First-line laboratory tests:

  • Pregnancy test (to rule out pregnancy-related bleeding)
  • TSH (to rule out thyroid dysfunction)
  • Prolactin (abnormal if >20 μg/L)
  • FSH and LH (FSH >35 IU/L indicates ovarian failure)
  • Estradiol
  • Complete blood count (to assess for anemia) 1

• Additional testing based on clinical suspicion:

  • Testosterone and androgen profile if PCOS is suspected
  • Fasting glucose/insulin if metabolic issues are suspected
  • Anti-Müllerian hormone (AMH) for ovarian reserve assessment 1

Imaging

• Transvaginal ultrasound (preferred in sexually active patients) to:

  • Evaluate endometrial thickness
  • Assess for structural causes (polyps, fibroids, adenomyosis)
  • Evaluate ovarian morphology (≥20 follicles per ovary and/or ovarian volume ≥10ml suggests PCOS) 2, 1

• If endometrium cannot be completely evaluated by ultrasound, consider:

  • Endometrial sampling (especially in patients with risk factors for endometrial cancer)
  • MRI for better visualization of the endometrium 2

• Brain MRI with contrast if:

  • Hyperprolactinemia is present
  • Multiple pituitary hormone abnormalities are detected
  • Hypothalamic/pituitary abnormalities are suspected 1

Special Considerations

• In adolescents within 3 years of menarche, irregular cycles are common due to immature hypothalamic-pituitary-ovarian axis, but pathologic causes should still be considered 4, 5

• In patients with risk factors for endometrial cancer (obesity, chronic anovulation, PCOS), endometrial sampling should be considered 2

• If initial ultrasound is inconclusive and bleeding persists, consider:

  • Hysteroscopy to evaluate for endometrial lesions like polyps
  • Fractional dilation and curettage (D&C) under anesthesia if office endometrial biopsy is negative but symptoms persist 2

Pitfalls to Avoid

• Don't assume irregular menses in adolescents is always physiologic - treatable causes may be present 5
• Don't overlook systemic causes of menstrual irregularities (thyroid disease, hyperprolactinemia, etc.)
• Don't miss the diagnosis of pregnancy, which is a common cause of irregular bleeding
• Remember that a negative office endometrial biopsy has a false-negative rate of approximately 10% 2
• Consider that menstrual irregularities may be associated with serious health conditions including metabolic syndrome, coronary heart disease, and type 2 diabetes 6

By following this systematic approach to the workup of irregular menstrual periods, clinicians can identify the underlying cause and initiate appropriate treatment to improve patient outcomes and quality of life.