What laboratory tests should be run for a patient with abnormal periods?

Laboratory Tests for Abnormal Periods

For patients with abnormal periods, a comprehensive laboratory workup should include LH, FSH, prolactin, progesterone, testosterone, androstenedione, DHEAS, glucose/insulin levels, and thyroid function tests, with consideration for pelvic ultrasound in cases with suspected structural abnormalities. 1

Initial Laboratory Evaluation

Hormonal Assessment

• LH and FSH: Measure serum levels between days 3-6 of cycle (average of three estimations taken 20 minutes apart)

  • Abnormal findings: LH/FSH ratio >2, FSH >35 IU/l, LH >11 IU/l, or LH <7 IU/ml 1
  • Critical for diagnosing PCOS, premature ovarian insufficiency, and hypothalamic amenorrhea

• Prolactin: Measure morning resting serum levels (not postictal)

  • Abnormal finding: >20 μg/l 1
  • May be elevated in patients with pituitary tumors or hypothyroidism
  • Medications may impact prolactin levels

• Progesterone: Measure during mid-luteal phase

  • Abnormal finding: <6 nmol/l indicates anovulation 1
  • Common causes: PCOS, hypophyseal adenoma, hyperprolactinemia

• Testosterone: Measure on days 3-6 of cycle

  • Abnormal finding: >2.5 nmol/l 1
  • Elevated in PCOS and with valproate use

• Androstenedione: Measure serum level

  • Abnormal finding: >10.0 nmol/l 1
  • Rule out adrenal/ovarian tumors if elevated

• DHEAS (Dehydroepiandrosterone sulfate): Measure serum level

  • Abnormal findings: Age 20-29 >3800 ng/ml, Age 30-39 >2700 ng/ml 1
  • Rule out non-classical congenital adrenal hyperplasia if elevated

Metabolic Assessment

• Glucose/insulin: Fasting, morning levels; calculate glucose/insulin ratio
  • Abnormal findings: Fasting glucose >7.8 mmol/l, Glucose/insulin ratio >4 1
  • Suggestive of diabetes or reduced insulin sensitivity
  • Associated with obesity and PCOS

Thyroid Function

• Thyroid function tests: TSH, free T4
  • Important to rule out thyroid dysfunction as a cause of menstrual irregularities 1
  • TSH alone is often sufficient as the initial thyroid screening test 2

Imaging Studies

• Pelvic ultrasound: Transvaginal or transabdominal (day 3 to 9 of cycle)
  • Abnormal finding: >10 peripheral cysts, 2-8 mm diameter in one ultrasound plane, thickening of ovarian stroma 1
  • Helps diagnose polycystic ovaries and structural abnormalities
  • Transvaginal ultrasound is more sensitive than transabdominal for identifying ovarian pathology 1

Special Considerations

For Patients with Suspected Premature Ovarian Insufficiency (POI)

• Anti-Müllerian Hormone (AMH): Consider in patients with suspected diminished ovarian reserve
  • Low AMH levels indicate incipient ovarian insufficiency 1
  • Particularly useful for survivors of childhood cancer treated with alkylating agents or radiotherapy 1
  • Most reliable in women ≥25 years old 1

For Patients with Suspected Pregnancy

• Pregnancy testing: Consider in cases of:
  • Missed menses (unless using certain contraceptives)
  • Irregular bleeding
  • New onset pelvic pain
  • Enlarged uterus or adnexal mass on examination 1

Interpretation and Follow-up

1. Normal findings: If all laboratory tests are normal but menstrual irregularities persist, consider:

   • Stress-related hypothalamic dysfunction
   • Early stages of reproductive disorders
   • Structural abnormalities requiring further imaging

2. Abnormal findings: Refer to endocrinology or gynecology when:

   • Prepubertal females with no signs of puberty by age 13 years and elevated FSH
   • Postpubertal females with menstrual cycle dysfunction suggestive of POI
   • Laboratory evidence of significant hormonal imbalances 1

3. Monitoring: For patients with identified abnormalities, periodic reassessment of relevant laboratory values is recommended to track disease progression and treatment response.

Common Pitfalls to Avoid

• Failing to consider PCOS, which affects 4-6% of women in the general population and is a common cause of irregular periods 1
• Overlooking thyroid dysfunction, which can present with menstrual irregularities
• Not accounting for medication effects on hormone levels (e.g., valproate can increase testosterone)
• Relying solely on laboratory tests without correlating with clinical symptoms and menstrual history
• Testing at inappropriate times in the menstrual cycle, which can lead to misinterpretation of results

By following this structured approach to laboratory testing for abnormal periods, clinicians can effectively identify the underlying causes and develop appropriate management strategies for their patients.