What labs should be ordered for a 13-year-old female with irregular menstrual cycles (oligomenorrhea) since age 9, occurring twice a month, and asymmetric breast development (breast asymmetry)?

Laboratory Evaluation for a 13-Year-Old Female with Irregular Menstrual Cycles and Breast Asymmetry

For a 13-year-old female with irregular menstrual cycles since age 9 occurring twice monthly and breast asymmetry, a comprehensive laboratory workup should include LH, FSH, prolactin, progesterone, testosterone, androstenedione, DHEAS, glucose/insulin levels, and thyroid function tests, with pelvic ultrasound to evaluate for structural abnormalities. 1

Primary Laboratory Tests

Hormonal Evaluation

• LH and FSH: Measure between days 3-6 of cycle

  • Abnormal findings: LH/FSH ratio >2 (suggestive of PCOS)
  • Critical for diagnosing PCOS, premature ovarian insufficiency, or hypothalamic dysfunction 1

• Prolactin: Measure morning resting serum levels

  • Abnormal: >20 μg/l
  • May be elevated in pituitary tumors or hypothyroidism 2, 1

• Testosterone: Measure on days 3-6 of cycle

  • Abnormal: >2.5 nmol/l
  • Elevated in PCOS 1

• Progesterone: Measure during mid-luteal phase

  • Abnormal: <6 nmol/l indicates anovulation
  • Common in PCOS, hyperprolactinemia 2, 1

• Androstenedione: Measure serum levels

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

• DHEAS: Measure serum levels

  • Abnormal for age 13: Elevated levels
  • Rule out non-classical congenital adrenal hyperplasia if elevated 1

Metabolic Evaluation

• Fasting glucose/insulin levels

  • Abnormal: Fasting glucose >7.8 mmol/l, Glucose/insulin ratio >4
  • Suggestive of insulin resistance, associated with PCOS 1

• Thyroid function tests: TSH and free T4

  • Critical to rule out thyroid dysfunction as a cause of menstrual irregularities 1

Imaging Studies

• Pelvic ultrasound: Perform between days 3-9 of cycle

  • Transvaginal preferred if appropriate (more sensitive), otherwise transabdominal
  • Look for polycystic ovaries (>10 peripheral cysts, 2-8 mm diameter)
  • Also evaluates for structural abnormalities 2, 1

• Breast ultrasound: Consider for evaluation of breast asymmetry

  • Can identify masses, cysts, or developmental abnormalities 3, 4

Interpretation and Management Algorithm

1. If LH/FSH ratio >2 with elevated testosterone/androstenedione and polycystic ovaries on ultrasound:

   • Diagnosis: PCOS (most common cause of irregular periods in adolescents) 1, 5
   • Refer to endocrinology or gynecology for management

2. If elevated prolactin:

   • Consider pituitary MRI to rule out prolactinoma
   • Evaluate for medication effects and thyroid dysfunction 2, 1

3. If normal hormonal profile but persistent irregular cycles:

   • Consider stress-related hypothalamic dysfunction
   • Early stages of reproductive disorders
   • Structural abnormalities requiring further imaging 1

4. For breast asymmetry:

   • If associated with hormonal abnormalities: Likely related to endocrine disorder
   • If isolated finding: Consider normal physiologic variation versus Poland syndrome or other structural abnormality 4
   • Breast asymmetry during adolescence is common but should be evaluated when severe 4

Special Considerations

• Timing of evaluation: The patient's early menarche (age 9) with persistent irregular cycles for 4 years warrants investigation, as oligomenorrhea should normalize within 2-3 years after menarche 5

• Frequency of periods: Having cycles twice monthly (polymenorrhea) rather than infrequent cycles (oligomenorrhea) is unusual and suggests potential hormonal imbalance 2

• Breast asymmetry: While often physiologic during development, significant asymmetry may indicate underlying endocrine disorders or structural abnormalities 4

Common Pitfalls to Avoid

• Dismissing irregular periods as normal pubertal transition when they persist beyond 2-3 years after menarche
• Testing hormones at inappropriate times in the menstrual cycle
• Overlooking thyroid dysfunction as a cause of menstrual irregularities
• Failing to consider PCOS, which affects 4-6% of women and is a common cause of irregular periods 1
• Not correlating laboratory findings with clinical symptoms and menstrual history

Remember that early identification and management of hormonal disorders in adolescence can prevent long-term complications including infertility, metabolic disorders, and psychological distress.