What hormonal assays can be used to confirm perimenopause in a woman presenting with hot flushes?

Hormonal Assays to Confirm Perimenopause

Laboratory testing is generally not required to diagnose perimenopause in women presenting with hot flushes and menstrual irregularity, as the diagnosis is primarily clinical; however, when hormonal confirmation is needed, measure FSH and estradiol together, recognizing that these values fluctuate widely during perimenopause and a single measurement cannot reliably confirm or exclude the diagnosis. 1, 2

Clinical Diagnosis Takes Priority

• Perimenopause is diagnosed clinically based on age (typically 40s to early 50s), vasomotor symptoms like hot flushes, and menstrual cycle irregularity—not by hormone levels 2, 3
• The hormonal patterns in perimenopause vary dramatically both between women and within the same woman over time, making single measurements unreliable for diagnosis 4, 5
• Women can have postmenopausal FSH levels one week and ovulatory cycles the next, demonstrating the erratic nature of perimenopausal hormones 4, 6

When Hormonal Testing May Be Indicated

Check FSH and estradiol when:

• The woman is under age 45 and you need to distinguish perimenopause from other causes of menstrual irregularity 2
• The woman has had a hysterectomy (with intact ovaries) and cannot use menstrual patterns for diagnosis 1
• You are considering hormone therapy and need baseline assessment 2
• The woman has had chemotherapy and you need to assess ovarian function 7, 2

Specific Hormonal Patterns in Perimenopause

FSH levels:

• Typically elevated compared to reproductive-age women (range 4-32 IU/g Cr vs 3-7 IU/g Cr in younger women) but lower than postmenopausal levels (24-85 IU/g Cr) 5
• Can fluctuate into the postmenopausal range transiently, then return to normal—this pattern is characteristic of perimenopause 4
• Elevated FSH alone does not confirm perimenopause and does not predict proximity to menopause 6

Estradiol levels:

• Paradoxically often higher than in younger women (averaging 26% higher), not lower as commonly assumed 5, 6, 8
• Can surge erratically, with some women experiencing "luteal out of phase" events where estradiol spikes unexpectedly during the luteal phase 6
• Low estradiol combined with elevated FSH suggests approaching menopause, but this pattern alternates with normal or high estradiol in perimenopause 4, 5

Additional hormones to consider:

• LH: May be elevated (1.4-6.8 IU/g Cr vs 1.1-4.2 IU/g Cr in younger women) and can be checked as clinically indicated 2, 5
• Progesterone/pregnanediol: Typically decreased due to anovulatory cycles or short luteal phases, contributing to symptoms 5, 8
• Prolactin: Should be measured to rule out hyperprolactinemia as an alternative cause of menstrual irregularity 7, 2
• Anti-Müllerian hormone (AMH): May provide information about ovarian reserve but has limited normative data in perimenopause and is not routinely recommended 7, 2

Critical Pitfalls to Avoid

• Do not rely on a single FSH measurement to confirm or exclude perimenopause—values fluctuate too widely 4, 6
• Do not assume low estrogen is causing symptoms; perimenopausal women often have high, erratic estrogen levels 6, 8
• Do not use FSH to predict time to menopause—it is ineffective for this purpose 6
• Do not test women on tamoxifen, chemotherapy, or GnRH agonists without recognizing these medications make hormone levels unreliable 7, 1, 2
• Remember that ovulation can occur even with elevated FSH levels and irregular cycles, so contraception counseling remains important 4, 3

Practical Testing Algorithm

For women age 45-60 with hot flushes and irregular cycles:

1. Make the clinical diagnosis of perimenopause without testing if the presentation is typical 2, 3
2. If testing is needed, order FSH and estradiol simultaneously (not FSH alone) 1, 2
3. Interpret results in context: elevated FSH with low estradiol suggests late perimenopause; elevated FSH with normal/high estradiol is still consistent with perimenopause 4, 5
4. If results are indeterminate, consider serial measurements 4+ weeks apart rather than relying on a single value 1

For women under age 45:

• Testing is more important to distinguish perimenopause from premature ovarian insufficiency or other causes 2
• Measure FSH, estradiol, LH, and prolactin 7, 2

For women age 60 or older:

• No laboratory testing is required; age alone confirms postmenopausal status 1, 2