2. Diagnosis and Investigations
Pedagogy: This lesson uses diagnostic algorithm reasoning — training when to test and when NOT to test, a critical skill for avoiding unnecessary investigations in primary care.
Learning Objectives
- Explain why menopause is a clinical diagnosis in women aged over 45 with typical symptoms
- Identify the specific clinical scenarios in which FSH testing is indicated
- Interpret FSH results in context, including hormonal contraception and fluctuation caveats
- State when NOT to perform biochemical testing
Key Facts
Clinical Diagnosis in Women Aged ≥45
NICE NG23 (2024) and the ESE guideline (2025) recommend that in women over 45 presenting with typical symptoms including menstrual irregularity and vasomotor symptoms, the diagnosis of perimenopause or menopause is made clinically. Biochemical testing is not necessary for diagnosis in this age group (1,2).
When IS Biochemical Testing Indicated?
| Scenario | Investigation | Notes |
|---|---|---|
| Women <40 years with suspected POI | FSH on two occasions, 4–6 weeks apart | FSH >25 IU/L confirmatory; also check TFTs, karyotype, FMR1 |
| Women 40–45 years with diagnostic uncertainty | FSH may be considered | Measure at days 2–5 of cycle or after ≥40 days amenorrhoea |
| Women on hormonal contraception | FSH unreliable while on CHC/POP | Cannot interpret; consider stopping for 6 weeks with barrier method |
| Post-hysterectomy with ovarian conservation | FSH if symptoms suggest menopause | No menstrual marker available; biochemistry helpful |
Interpreting FSH
FSH fluctuates during the menopausal transition. A single elevated value does not confirm menopause. FSH >25 IU/L is strongly suggestive of perimenopause, but values should be interpreted alongside oestradiol levels. AMH testing is NOT recommended for routine menopause diagnosis (1,2).
Clinical Pearl
In women over 45 with typical symptoms: diagnose clinically. Do NOT order FSH. This is the single most important point for primary care — unnecessary testing delays treatment and creates confusion.
Clinical Pearl
FSH fluctuates in the perimenopause. A normal FSH does NOT exclude perimenopause in a symptomatic woman aged 40–45. If in doubt, repeat at 4–6 weeks or treat empirically.
Case-Based Examples
Case 1: 46-year-old requesting 'blood test for menopause'
Presentation: A 46-year-old presents with 6 months of irregular periods, occasional hot flushes, and difficulty sleeping. She requests a 'blood test to check if it's the menopause.' She takes no medications.
Question: Is FSH testing indicated? How would you manage this consultation?
Model Answer: At 46, she is over 45 with typical symptoms. Per NICE NG23, menopause/perimenopause is a clinical diagnosis — FSH testing is not required. Explain that her symptoms are consistent with perimenopause. Conduct a symptom assessment (MRS/Greene), discuss treatment options including HRT, lifestyle, and CBT. Perform a structured cardiometabolic assessment (QRISK3, BP, lipids, HbA1c). If she insists on testing, explain that FSH fluctuates and a normal result would not exclude perimenopause.
Case 2: 41-year-old on the combined pill with hot flushes
Presentation: A 41-year-old on Microgynon 30 for 12 years reports hot flushes during her pill-free week and reduced libido. She wonders if she is menopausal. Her mother had menopause at 42.
Question: How would you investigate and manage this patient?
Model Answer: FSH is unreliable on CHC due to HPO axis suppression. Options: (a) Stop CHC for 6–8 weeks, use barrier contraception, and check FSH (ideally days 2–5 of a withdrawal bleed or after 6 weeks amenorrhoea). If FSH >25 IU/L, repeat at 4–6 weeks. (b) Given family history of early menopause and age 40–45, consider switching to HRT + separate contraception if symptoms are troublesome. The 52 mg LNG-IUD provides both contraception and endometrial protection within an HRT regimen. Refer for specialist input if FSH confirms early menopause given implications for bone, cardiovascular, and cognitive health.
Self-Assessment Questions
PLAB/MLA When to test FSH
A 48-year-old with hot flushes and 10 months amenorrhoea attends. She takes no medications. Which is MOST appropriate?
A. Check FSH and oestradiol
B. Check AMH level
C. Diagnose clinically without biochemical testing
D. Request thyroid function tests only
Answer: C. Over 45 with typical symptoms: clinical diagnosis. FSH not required (NICE NG23).
MRCGP FSH interpretation on hormonal contraception
A 43-year-old on desogestrel (POP) reports hot flushes. Her FSH is 18 IU/L. How do you interpret this result and what is your next step?
A. FSH is normal — she is not menopausal
B. FSH is unreliable on the POP; consider stopping for 6 weeks and retesting
C. FSH confirms perimenopause — start HRT immediately
D. Check AMH instead as it is more reliable on contraception
Answer: B. FSH is suppressed by progestogen-only contraception and cannot be reliably interpreted. Stop POP for 6–8 weeks with barrier method, then recheck FSH. AMH is not recommended for menopause diagnosis.
Professor Limitations of FSH as a diagnostic biomarker
Discuss the limitations of serum FSH as a diagnostic biomarker for the menopausal transition and evaluate whether AMH trajectory modelling could offer a superior approach.
A. FSH is perfectly reliable and AMH adds no value
B. FSH fluctuates widely in perimenopause, is suppressed by hormonal contraception, and has poor specificity; AMH declines monotonically but lacks standardised assays and prospective validation for clinical diagnosis
C. AMH has replaced FSH in all international guidelines
D. Both FSH and AMH are equally unreliable
Answer: B. FSH has inherent limitations: wide fluctuation in perimenopause, suppression by exogenous hormones, and a single threshold cannot define a dynamic transition. AMH declines monotonically and is the earliest marker of ovarian reserve, but international assay standardisation is recent, prospective FMP prediction models require further validation, and no guideline currently recommends AMH for routine menopause diagnosis.
Take-Away Messages
- Menopause is a clinical diagnosis in women ≥45 — do NOT order FSH routinely
- FSH testing is indicated for: suspected POI (<40), diagnostic uncertainty (40–45), post-hysterectomy with ovarian conservation
- FSH cannot be interpreted on hormonal contraception — stop for 6–8 weeks first
- AMH is NOT recommended for routine menopause diagnosis
- A normal FSH does NOT exclude perimenopause in a symptomatic woman