Laboratory Workup for Perimenopausal Women
The core laboratory workup for perimenopause should include FSH, LH, estradiol (measured on cycle days 3-6 when possible), and prolactin, with thyroid function tests added to rule out thyroid disease that commonly mimics menopausal symptoms. 1, 2
Essential Laboratory Tests
Primary Hormone Panel
- FSH, LH, and estradiol should be measured during the early follicular phase (days 3-6 of the menstrual cycle) for accurate assessment 1
- Prolactin must be checked to exclude hyperprolactinemia as a cause of menstrual irregularity 1, 2
- These tests should be performed without hormonal contraception or hormone replacement therapy for accurate interpretation 1
Critical Caveat About FSH
- A single FSH level is unreliable for diagnosing perimenopause because FSH fluctuates significantly during this transition 1, 2, 3
- A normal FSH does not rule out perimenopause, and an elevated FSH does not confirm it 1, 3
- FSH is particularly unreliable in women with prior chemotherapy, pelvic radiation, or those on tamoxifen 1
Thyroid Assessment
- Thyroid function tests are mandatory to rule out thyroid disease, which frequently mimics menopausal symptoms and is commonly diagnosed at midlife 1, 4
- Subclinical hypothyroidism occurs in 18% of perimenopausal women and is associated with dyslipidemia and cardiovascular risk 4
Additional Tests Based on Clinical Presentation
Metabolic Screening
- Fasting glucose or hemoglobin A1c should be checked if insulin resistance is suspected, particularly with weight gain 1, 2
- Fasting lipid profile is recommended for cardiovascular risk assessment 5
Ovarian Reserve Markers
- Anti-Müllerian hormone (AMH) may provide supplementary information on ovarian status but should be interpreted cautiously and never used alone for diagnosis 1, 2
- Inhibin levels can offer additional ovarian status information but are not reliable as standalone markers 1, 2
- Serial estradiol levels are useful when women become amenorrheic and later develop bleeding, to determine return of ovarian function 1, 2
Androgen Assessment
- Testosterone levels should be measured if hirsutism or other signs of hyperandrogenism are present 1
Interpretation Framework
Clinical Context Is Paramount
- Laboratory results must be interpreted alongside menstrual history and symptoms—perimenopause is primarily a clinical diagnosis 1, 2, 3
- Menstrual irregularity (cycles <23 days or >35 days) is the key clinical indicator 1
- No single symptom or test is accurate enough to rule in or rule out perimenopause 3
Expected Hormonal Patterns
- Perimenopausal women typically show elevated FSH and LH, hyperestrogenism in early phases, and decreased luteal phase progesterone 6
- Follicular phases are shorter (11 vs. 14 days in younger women) 6
- Estrone conjugate excretion is often elevated compared to younger reproductive-aged women 6
Common Pitfalls to Avoid
Testing Errors
- Do not rely on a single FSH measurement to make or exclude the diagnosis 1, 3
- Do not test while on hormonal contraception or HRT—this invalidates results 1
- Do not use AMH alone for diagnosis, especially in women under 25 where normal ranges are extremely wide 1
Clinical Misinterpretation
- Self-assessment of perimenopausal status combined with age is more useful than isolated lab values (likelihood ratio 1.53-2.13) 3
- Hot flashes (likelihood ratio 2.15-4.06) and night sweats (likelihood ratio 1.90) are more diagnostically useful than most laboratory tests 3
When to Refer
- Endocrinology or gynecology referral is indicated for persistently abnormal hormone levels, delayed puberty, or confirmed hypogonadism 1
- Reproductive endocrinology consultation is recommended for fertility preservation concerns or infertility evaluation 1
- Specialist referral should be considered for severe or persistent symptoms significantly affecting quality of life 1