Secondary Amenorrhoea Evaluation
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Direct answer
Secondary amenorrhoea is the cessation of menses for about three months in a woman who previously had regular cycles. Its evaluation localises the cause by excluding pregnancy, checking thyroid function and prolactin, then using a progesterone challenge and FSH to separate outflow, ovarian and hypothalamic-pituitary causes. Polycystic ovary syndrome is among the commonest causes, and hyperprolactinaemia and premature ovarian insufficiency must always be considered.
What you must remember
- Definition: no menses for about three months after previously regular cycles, with pregnancy excluded first.
- Pregnancy first: every woman with amenorrhoea has a pregnancy test before any other step, including the progesterone challenge.
- Progesterone challenge: medroxyprogesterone acetate 10 mg daily for 5 to 10 days; a withdrawal bleed means adequate oestrogen and a patent outflow tract.
- Interpretation of FSH: raised FSH with low oestradiol indicates ovarian failure, while low FSH with low oestradiol indicates a hypothalamic or pituitary cause.
- PCOS: raised LH to FSH ratio, hyperandrogenism and polycystic ovaries on ultrasound; it is a leading cause of anovulation in reproductive-age women.
- Hyperprolactinaemia and hypothyroidism: both are reversible and must be excluded by checking prolactin and TSH in every case.
- Asherman syndrome: intrauterine adhesions after curettage or infection, suggested by a negative progestogen challenge with normal FSH and oestrogen levels, and confirmed by hysteroscopy.
- Sheehan syndrome: pituitary infarction after severe postpartum haemorrhage with hypotension, causing amenorrhoea and failure of lactation.
A sequence that localises the cause
The evaluation runs in a fixed order, so each result narrows the list before the next test is ordered. The steps below are the usual textbook sequence.
- Exclude pregnancy: check urine or serum hCG first, because treatment, imaging and medication decisions depend on it.
- Check thyroid and prolactin: TSH and prolactin are measured in every case, since hypothyroidism and hyperprolactinaemia are reversible and both suppress ovulation.
- Give a progesterone challenge: medroxyprogesterone acetate 10 mg daily for 5 to 10 days; a withdrawal bleed within a few days of stopping indicates adequate oestrogen and a patent outflow tract.
- Interpret a negative challenge: no bleed means either low oestrogen or outflow obstruction, so an oestrogen-then-progestogen priming test follows; a bleed after priming points to low endogenous oestrogen, while no bleed suggests Asherman syndrome.
- Measure FSH, LH and oestradiol: raised FSH with low oestradiol indicates ovarian failure, low FSH indicates hypothalamic or pituitary dysfunction, and a raised LH to FSH ratio with androgen excess suggests PCOS.
- Image and scope: pelvic ultrasound assesses the ovaries and endometrium, hysteroscopy is used when adhesions are suspected, and pituitary MRI is reserved for markedly raised prolactin.
Where the exam tests the sequence
Most errors come from skipping a step or reading one test in isolation.
- Trap: Starting hormone therapy before a pregnancy test Correct: Pregnancy is excluded first in every woman with amenorrhoea, because treatment and imaging decisions can harm a pregnancy.
- Trap: Reading a withdrawal bleed as proof of normal ovaries Correct: It shows endogenous oestrogen and a patent outflow tract, but not ovulation or fertility.
- Trap: Ordering FSH without oestradiol Correct: Interpret FSH alongside oestradiol; raised FSH with low oestrogen separates ovarian failure from hypothalamic causes.
- Trap: Labelling hypothalamic amenorrhoea before checking prolactin and TSH Correct: Hyperprolactinaemia and thyroid disease mimic hypothalamic failure, so both are excluded first.
Frequently asked questions
What does a positive progesterone challenge test indicate?
A withdrawal bleed within a few days of stopping medroxyprogesterone acetate shows that endogenous oestrogen is adequate and the outflow tract is patent. This points to anovulation, such as PCOS, rather than to outflow obstruction or oestrogen deficiency.
Which investigation confirms Asherman syndrome?
Hysteroscopy is the diagnostic test for Asherman syndrome, because it directly visualises intrauterine adhesions. Adhesions are often suspected after curettage or infection, and hysteroscopic adhesiolysis is the usual treatment.
Why is a raised LH to FSH ratio suggestive of PCOS?
In PCOS the LH to FSH ratio is often raised, typically above 2 to 1, reflecting increased GnRH pulse frequency. This finding is most useful alongside hyperandrogenism and polycystic ovaries on ultrasound.
Can Sheehan syndrome cause secondary amenorrhoea?
Yes, Sheehan syndrome is pituitary infarction after severe postpartum haemorrhage with hypotension, which reduces gonadotrophins and prolactin. The result is amenorrhoea and failure of lactation, and it should be considered in any woman with these features after delivery.