What hormone labs should be drawn for a woman with menstrual migraine (late luteal phase day 21‑23 of a 28‑day cycle) to assess estrogen withdrawal, reproductive axis, thyroid function, and possible PCOS?

Hormone Laboratory Testing for Menstrual Migraine

For a woman with late luteal phase menstrual migraine (days 21-23), draw the following hormone panel: TSH, free T4, prolactin, LH, FSH, estradiol, progesterone (mid-luteal phase), total testosterone, and DHEA-S. This comprehensive panel assesses thyroid function, reproductive axis integrity, estrogen withdrawal patterns, and screens for PCOS—all critical factors in menstrual migraine pathophysiology 1.

Timing and Rationale for Each Test

Core Reproductive Axis Assessment

Draw these labs during the early follicular phase (days 3-6):

• LH and FSH: Calculate based on an average of three measurements taken 20 minutes apart to assess for PCOS (LH/FSH ratio >2 suggests PCOS) or hypothalamic amenorrhea (both low) 2
• Total testosterone: Values >2.5 nmol/L indicate hyperandrogenism, common in PCOS 2
• DHEA-S: Elevated levels suggest adrenal androgen excess and help rule out non-classical congenital adrenal hyperplasia 2

Draw progesterone during mid-luteal phase (days 21-23):

• This timing is critical for your patient since symptoms occur in late luteal phase
• Levels <6 nmol/l indicate anovulation, a hallmark of PCOS 2
• Low progesterone combined with estrogen withdrawal triggers menstrual migraine 3, 4

Draw estradiol during both follicular and luteal phases if possible:

• Research demonstrates that luteal estrogen levels are significantly reduced in female migraineurs compared to controls 3
• The estrogen withdrawal in late luteal phase (when your patient experiences attacks) is a key trigger mechanism 4, 5

Thyroid Function Assessment

TSH and free T4 (any time):

• Essential to exclude thyroid dysfunction, which commonly coexists with menstrual irregularities and can exacerbate migraine 1
• Hypothyroidism may elevate prolactin levels and worsen reproductive dysfunction 2

Prolactin Assessment

Morning resting prolactin (not post-ictal):

• Values >20 μg/L are abnormal 2
• Hyperprolactinemia causes anovulation and menstrual irregularity
• Rule out hypothyroidism or pituitary tumor if elevated 2

PCOS Screening Considerations

Given the overlap between menstrual migraine and PCOS risk factors, additional metabolic screening is warranted:

Fasting glucose and insulin:

• Fasting glucose >7.8 mmol/L or glucose/insulin ratio >4 suggests insulin resistance 2
• PCOS affects 4-6% of the general population but is more common in women with reproductive dysfunction 2

Consider adding:

• Androstenedione if testosterone is elevated (>10.0 nmol/L rules out adrenal/ovarian tumor) 2
• 8 AM 17-hydroxyprogesterone if high-risk ethnicity (Ashkenazi, Hispanic, Slavic) or family history of congenital adrenal hyperplasia 6, 7

Critical Timing and Laboratory Pitfalls

Use a reliable specialty laboratory for testosterone measurements. Many commercial laboratories provide inaccurate normal ranges for female testosterone levels, which fall in the low range of assay detection 6. If initial total testosterone is normal but clinical suspicion for hyperandrogenism remains high, repeat with both total and free testosterone in a specialty laboratory 7.

Avoid drawing prolactin post-ictally (after a migraine attack), as seizure activity or stress can falsely elevate levels 2. Draw in the morning at rest.

For women with regular 28-day cycles, standardize timing: days 3-6 for LH/FSH/testosterone, and days 21-23 for progesterone 2, 7. This ensures accurate interpretation against established reference ranges.

Pattern Recognition for Diagnosis

The hormone pattern helps differentiate conditions:

• PCOS: LH/FSH >2, elevated testosterone, low mid-luteal progesterone, normal or high AMH 1, 8
• Hypothalamic amenorrhea: Low LH and FSH, low estradiol (<50 pg/mL), low progesterone 1
• Hyperprolactinemia: Elevated prolactin, low LH/FSH, low estradiol 1
• Menstrual migraine: Reduced luteal estrogen and progesterone compared to controls, with symptoms triggered by hormone withdrawal 3, 4

Additional Considerations

Research shows that estrogen levels are reduced in the luteal phase of female migraineurs compared to controls (effect size g = -0.60, p <0.001) 3. Furthermore, early diurnal cortisol is elevated in migraineurs (g = 0.32, p = 0.036), suggesting hypothalamic-pituitary-adrenal axis dysregulation 3. While routine cortisol testing isn't standard for menstrual migraine workup, it may be considered if stress-related symptoms are prominent.

The evidence consistently demonstrates that dynamic fluctuations in estrogen and progesterone are key triggers for menstrual migraine, with falling levels precipitating attacks 5, 9. Your patient's late luteal timing (days 21-23) corresponds precisely to the physiologic estrogen and progesterone withdrawal that precedes menstruation.