What is the appropriate workup and treatment for an 18-year-old female with irregular periods?

Workup for an 18-Year-Old Female with Irregular Periods

Begin with pregnancy testing (beta-hCG) if sexually active or clinically indicated, followed by thyroid function (TSH, free T4) and prolactin levels, as these are the most common endocrine causes of menstrual irregularity in adolescents. 1

Initial Diagnostic Evaluation

Mandatory Laboratory Tests

• Pregnancy test (beta-hCG) is required even if the patient reports irregular patterns, as pregnancy must be ruled out first 1, 2
• Thyroid function tests (TSH, free T4) should be checked, as thyroid dysfunction commonly causes ovulatory dysfunction presenting with irregular cycles 3, 1
• Prolactin level measurement is essential, as hyperprolactinemia is a frequent cause of menstrual irregularity 3, 1

Additional Screening

• Screen for sexually transmitted infections that can alter bleeding patterns 1, 2
• Complete blood count to assess for anemia if heavy bleeding is present 4

When to Pursue Further Hormonal Evaluation

• If cycles are <21 days (polymenorrhea), proceed with full hormonal evaluation including LH, FSH, and testosterone even if pelvic ultrasound is normal 1
• LH/FSH ratio >2 suggests polycystic ovary syndrome (PCOS), which is a frequent cause of menstrual disorders in adolescent girls 3, 5
• Testosterone >2.5 nmol/L may indicate PCOS or other androgen excess 3

Clinical History Priorities

Key Elements to Assess

• Menstrual pattern specifics: cycle length, duration, flow volume 1
  • Normal adolescent cycles range 21-45 days (wider than adult range) 1
  • Document if <23 days (polymenorrhea), >35 days (oligomenorrhea), or absent >6 months (amenorrhea) 3
• Signs of androgen excess: hirsutism, acne, male-pattern hair distribution 3
• Weight changes and body mass index: obesity and truncal obesity (waist/hip ratio >0.9) suggest PCOS 3
• Athletic activity level and eating patterns: excessive exercise, restrictive eating, or stress may indicate hypothalamic amenorrhea 6
• Galactorrhea or nipple discharge: suggests hyperprolactinemia 3

Imaging Considerations

Pelvic Ultrasound Indications

• Transvaginal ultrasound (or transabdominal if not sexually active) is indicated if clinical features or hormonal tests raise concern about ovarian pathology 3
• Consider imaging if structural abnormalities are suspected (polyps, fibroids, adenomyosis) based on bleeding pattern 3, 2
• Polycystic ovarian morphology on ultrasound supports PCOS diagnosis when combined with clinical and hormonal findings 3

When Imaging Is NOT Initially Required

• In adolescents with irregular cycles within the first 2-3 years after menarche and normal hormonal evaluation, imaging may be deferred as anovulation due to hypothalamic-pituitary-ovarian axis immaturity is common 5, 7

Management Based on Findings

If Hormonal Evaluation Is Normal

• NSAIDs as first-line treatment for symptomatic bleeding: mefenamic acid 500 mg three times daily for 5 days during bleeding episodes 1
• Alternative NSAIDs include naproxen 440-550 mg every 12 hours or ibuprofen 600-800 mg every 6-8 hours with food 1

If NSAIDs Fail or Contraception Desired

• Low-dose combined oral contraceptives (COCs) with 30-35 μg ethinyl estradiol plus levonorgestrel or norgestimate provide cycle regulation 1
• COCs are completely reversible with no negative effect on long-term fertility and are safe throughout reproductive years 1

If Hypothalamic Amenorrhea Suspected

• Address underlying causes first: stress, nutritional deficiency, excessive exercise, eating disorders 6
• Optimize energy availability (>30 kcal/kg fat-free mass/day) as first-line treatment 6
• Do NOT use COCPs for bone protection in functional hypothalamic amenorrhea, as they do not correct the underlying cause and do not protect against bone mineral density loss 6
• If bone protection needed, use transdermal β-estradiol patch (100 μg) twice weekly plus cyclic micronized progesterone (200 mg) for 12 days each month 6

Critical Pitfalls to Avoid

• Never assume functional bleeding without excluding structural pathology, especially if bleeding persists beyond 3 years post-menarche 3, 2
• Do not accept amenorrhea as normal in athletes—amenorrhea for more than 3 months must be investigated 6
• Avoid using oral contraceptives to mask menstrual dysfunction without first identifying the underlying cause, as they hide clinical signs of low energy availability and other endocrine disorders 6
• If irregular bleeding persists despite treatment, rule out pregnancy, STDs, and structural uterine pathology (polyps, fibroids, malignancy) before assuming benign etiology 8

Follow-Up Strategy

• Monitor response within 1-2 cycles after initiating treatment 1
• Reassess if bleeding remains unacceptable to the patient despite treatment, and counsel on alternative methods 1
• Enhanced counseling about expected bleeding patterns significantly reduces treatment discontinuation rates 2

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