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Amenorrhoea
Why establishing the cause of amenorrhoea is crucial
When periods stop and what the body may be saying
Clinical review September 2026
When a period does not arrive, the calendar can become surprisingly loud. Amenorrhoea means absent periods; it is a description, not a diagnosis. Sometimes it is expected, as in pregnancy, breastfeeding or after menopause. At other times it is the body’s way of signalling that the usual brain–ovary–uterus conversation has been interrupted.
First, establish the type of amenorrhoea
Primary amenorrhoea means periods have not begun by the expected age; secondary amenorrhoea means periods that were previously present have stopped, commonly for three months or more if cycles were regular, or six months if they were already irregular. These are useful clinical signposts, not rules for delaying care when something feels wrong.
Pregnancy is the first possibility to check in anyone who could be pregnant, even when contraception has been used. Hormonal contraception can also change bleeding patterns or stop periods altogether; that may be expected, but it is still worth knowing which effect belongs to the treatment and which needs another explanation.
The cycle needs several departments to cooperate
The hypothalamus in the brain sets the rhythm, the pituitary sends hormonal messages, the ovaries make oestrogen and progesterone, and the uterus responds. A delay at any point can change bleeding. Common causes include PCOS, changes in weight or energy availability, intense exercise, stress, thyroid disease, raised prolactin, certain medicines and premature ovarian insufficiency. The word “stress” here is biological as well as emotional; the body is not being dramatic, merely economical.
A careful history often does as much work as a blood test: previous cycle pattern, pregnancy possibility, eating and exercise changes, headaches or visual symptoms, nipple discharge, hot flushes, new hair growth or acne, and medication history all help narrow the map. Tests may include pregnancy, thyroid, prolactin and gonadotrophin/oestradiol measurements; ultrasound is useful in selected situations rather than as a reflex.
Why it is worth understanding the cause
Infrequent ovulation can leave the womb lining without the usual progesterone-led shedding. For some people with longstanding infrequent periods, planned bleeding or progestogen protection is important. Low oestrogen from hypothalamic amenorrhoea or premature ovarian insufficiency can affect bone health, which is why the solution is not simply to persuade the uterus to produce a period while ignoring the original message.
Management follows the cause. It might involve addressing energy availability and support around eating or exercise, treating thyroid or prolactin disease, protecting the endometrium in PCOS, or discussing hormone replacement and fertility support in premature ovarian insufficiency. A “normal” bleed on hormonal treatment can be useful, but it does not always tell us whether ovulation has returned.
When not to wait
Seek prompt medical advice for severe headache, visual changes, milky nipple discharge not related to breastfeeding, sudden virilisation, pelvic pain, or a positive pregnancy test with pain or bleeding. Amenorrhoea is often treatable; the trick is to treat the right chapter of the story.
Important safety note
This page is for general education and cannot replace individual medical advice. Seek urgent help for severe symptoms, possible pregnancy with pain or bleeding, collapse, confusion, seizure, or any situation in which you feel acutely unwell. A clinician who knows your history can help tailor investigation and treatment.
Further reading
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