What lab tests are used to diagnose premenopause?

Laboratory Tests for Diagnosing Perimenopause

The most appropriate laboratory tests for diagnosing perimenopause include follicle-stimulating hormone (FSH) and estradiol levels, measured during the early follicular phase (days 2-5) of the menstrual cycle for women who are still menstruating. 1

Key Diagnostic Laboratory Tests

Primary Tests

• FSH levels:

  • Should be >40 IU/L for perimenopause diagnosis 1
  • Must be measured during early follicular phase (days 2-5) for women still menstruating 1
  • Can be measured randomly in women with amenorrhea 1
  • Two elevated serum FSH levels in the menopausal range are needed for diagnosis of premature ovarian insufficiency 1

• Estradiol levels:

  • Levels <30 pg/mL suggest perimenopause 1
  • Unlike menopause (characterized by consistently low estradiol), perimenopause often shows erratically higher and fluctuating estradiol levels 2, 3

Additional Helpful Tests

• Inhibin B levels: Low levels can support perimenopause diagnosis (positive likelihood ratio 2.05) 4
• Anti-Müllerian hormone (AMH): May be more predictive of menopause proximity than FSH or Inhibin B 2

Interpreting Laboratory Results in Perimenopause

Perimenopause is characterized by three major hormonal patterns that distinguish it from menopause:

1. Erratically higher estradiol levels - not consistently low as in menopause 2
2. Decreased progesterone levels - even in normally ovulatory cycles 2, 5
3. Disturbed ovarian-pituitary-hypothalamic feedback 2

Important Considerations for Test Interpretation

• Laboratory values alone are insufficient for diagnosis - clinical symptoms and age must be considered 4
• Approximately one-third of perimenopausal cycles have a major surge in estradiol during the luteal phase (called "luteal out of phase" or LOOP events) 2
• Perimenopausal women typically show:
  • Higher FSH than premenopausal women but lower than postmenopausal women 5
  • Higher LH than premenopausal women but lower than postmenopausal women 5
  • Higher overall estrone excretion compared to both pre- and postmenopausal women 5
  • Decreased luteal phase progesterone excretion compared to premenopausal women 5

Clinical Context for Laboratory Testing

Laboratory testing should be considered alongside:

• Age: The prior probability of perimenopause is directly related to a woman's age 4
• Menstrual history: Irregular periods or amenorrhea for 3-11 months 4
• Vasomotor symptoms: Hot flashes (positive likelihood ratio 2.15-4.06) and night sweats (positive likelihood ratio 1.90) 4
• Urogenital symptoms: Vaginal dryness (positive likelihood ratio 1.48-3.79) 4

Pitfalls to Avoid

• Relying solely on FSH or Inhibin B levels to predict menopause proximity has been documented to be ineffective 2
• A single hormone measurement may be misleading due to the fluctuating nature of hormones during perimenopause 2, 3
• Testing during different phases of the menstrual cycle can significantly affect results 1

Follow-up Testing

For women with suspected perimenopause who have risk factors for bone loss, a baseline bone mineral density assessment using DXA is recommended 1. This is particularly important as the decline in estrogen during perimenopause accelerates bone loss, estimated at 2% per year during the first 5 years after menopause 1.

Remember that laboratory testing should complement clinical assessment, as no single test is accurate enough by itself to definitively diagnose perimenopause 4.