What initial laboratory tests are recommended for a patient presenting with irregular periods and acne?

Initial Laboratory Tests for Patients with Irregular Periods and Acne

For patients presenting with irregular periods and acne, the recommended initial laboratory tests should include LH, FSH, testosterone, androstenedione, DHEA-S, and prolactin to evaluate for underlying hormonal causes, particularly polycystic ovary syndrome (PCOS). 1

Hormonal Evaluation Algorithm

First-Line Laboratory Tests:

• LH and FSH measurements (calculate LH/FSH ratio)
• Total and free testosterone
• Androstenedione
• DHEA-S (Dehydroepiandrosterone sulfate)
• Prolactin
• Fasting glucose and insulin (calculate glucose/insulin ratio)

Additional Tests Based on Initial Results:

• Thyroid function tests if irregular periods are present
• Pelvic ultrasound (transvaginal or transabdominal) if PCOS is suspected
• Progesterone (mid-luteal phase) to assess for ovulation

Rationale for Testing

The combination of irregular periods and acne strongly suggests an underlying hormonal imbalance, particularly PCOS, which affects approximately 4-6% of women in the general population 1. Laboratory evaluation is specifically recommended for patients who have acne with additional signs of androgen excess 1.

Key Diagnostic Findings:

• LH/FSH ratio >2 suggests PCOS 1
• Elevated testosterone (>2.5 nmol/l) is common in PCOS 1
• Elevated androstenedione (>10.0 nmol/l) may indicate adrenal/ovarian tumors 1
• Elevated DHEA-S may indicate adrenal hyperplasia 1
• Glucose/insulin ratio >4 suggests reduced insulin sensitivity, associated with PCOS 1

Clinical Significance

Research has consistently shown a high prevalence of hormonal abnormalities in women with acne and irregular periods:

• 90.4% of women with acne may have elevated total testosterone levels 2
• 66.65% of women with acne may have anovulatory patterns 2
• Women with late-onset or persistent acne have a high prevalence of polycystic ovaries 3

Important Considerations

• Timing matters: LH, FSH, testosterone, and androstenedione should be measured between days 3-6 of the menstrual cycle 1
• Progesterone should be measured during the mid-luteal phase 1
• Prolactin should be measured in the morning at rest (not postictal) 1
• Routine microbiologic testing is not recommended for acne unless Gram-negative folliculitis is suspected 1

Common Pitfalls to Avoid

1. Not timing hormone tests appropriately with the menstrual cycle can lead to misinterpretation of results
2. Overlooking PCOS as a common cause of both acne and menstrual irregularities
3. Focusing only on acne treatment without addressing the underlying hormonal cause
4. Ordering unnecessary microbiologic testing for acne, which is not recommended by guidelines 1
5. Failing to calculate ratios (LH/FSH, glucose/insulin) that are important diagnostic indicators

By following this structured approach to laboratory testing, clinicians can effectively identify underlying hormonal causes of irregular periods and acne, particularly PCOS, which requires specific management approaches to improve both symptoms and long-term health outcomes.