Laboratory Testing for Hot Flashes
For a patient presenting with hot flashes, obtain TSH to rule out thyroid dysfunction, and consider FSH/estradiol only if menopausal status is uncertain; routine laboratory testing beyond this is generally unnecessary unless clinical features suggest a specific secondary cause.
Essential Laboratory Tests
Thyroid Function Testing
- TSH should be measured in all patients with hot flashes to exclude hyperthyroidism and hypothyroidism, both of which can cause or contribute to vasomotor symptoms 1
- Thyroid dysfunction is a well-established secondary cause of hot flashes that requires disease-specific treatment 2
Menopausal Status Confirmation (When Uncertain)
- FSH and estradiol levels can be obtained if menopausal status is unclear based on history alone (e.g., in younger women, those with prior hysterectomy, or those on hormonal contraception) 2
- However, these tests are not routinely necessary when menopause is clinically evident from age and amenorrhea history 3, 4
- Importantly, estrogen levels do not differ between symptomatic and asymptomatic menopausal women, so they do not predict hot flash severity 4
Additional Testing for Atypical Presentations
When to Suspect Secondary Causes
Consider expanded laboratory evaluation when hot flashes present with:
- Atypical features (unilateral flushing, associated diarrhea, wheezing, or skin changes) 2
- Lack of response to standard treatments 2
- Occurrence in men or premenopausal women without clear etiology 1, 2
Specific Tests for Secondary Causes
Based on clinical suspicion, obtain:
- 24-hour urine 5-HIAA for carcinoid syndrome (if diarrhea, wheezing, or right-sided heart disease present) 2
- Plasma or 24-hour urine metanephrines for pheochromocytoma (if hypertension, headaches, or palpitations present) 2
- Serum calcitonin for medullary thyroid carcinoma (if thyroid nodule or family history present) 2
- Serum tryptase for systemic mastocytosis (if urticaria, pruritus, or anaphylaxis present) 2
- Morning total and free testosterone in men with hot flashes to assess for hypogonadism (draw between 8-10 AM) 1
What NOT to Routinely Order
- Complete metabolic panels, CBC, liver function tests are not indicated specifically for hot flashes unless part of general health screening or suggested by other symptoms 1, 2
- Norepinephrine metabolites (3-methoxy-4-hydroxyphenylglycol, vanillylmandelic acid) are research tools, not clinically useful 5
Clinical Pitfalls to Avoid
- Do not assume all hot flashes are menopausal - maintain high suspicion for secondary causes in atypical presentations 2
- Do not over-test - the vast majority of perimenopausal/postmenopausal women with typical hot flashes require only TSH testing 2, 4
- Do not use hormone levels to guide treatment decisions in confirmed menopausal women, as levels do not correlate with symptom severity 4