Overview
Amenorrhoea means the absence of menstrual periods. Doctors describe two types. Primary amenorrhoea is when periods have not started by age 15, or within five years of breast development. Secondary amenorrhoea is when periods that were previously regular stop for three months or more, or irregular periods stop for six months or more.
Amenorrhoea is a symptom, not a disease in itself. The most common cause in women of reproductive age is pregnancy. Other causes include breastfeeding, menopause, low body weight, excessive exercise, stress, polycystic ovary syndrome, thyroid problems and conditions affecting the pituitary gland or ovaries. Finding and treating the cause is important, because some causes affect fertility and long-term bone and heart health.
When to get urgent help
Seek urgent care for severe pelvic pain with a missed period (possible ectopic pregnancy), sudden severe headache with visual loss, or symptoms of an eating disorder with fainting or palpitations.
Causes and risk factors
Natural causes: pregnancy, breastfeeding and menopause.
Hypothalamic causes (the brain's control centre):
- Low body weight, eating disorders and rapid weight loss
- Excessive exercise, common in athletes and dancers
- Psychological stress
- Serious illness
Pituitary causes:
- Prolactinoma (a benign pituitary tumour producing prolactin)
- Other pituitary tumours, surgery or damage, including Sheehan's syndrome after severe postpartum bleeding
Ovarian causes:
- Polycystic ovary syndrome (PCOS)
- Premature ovarian insufficiency
- Turner syndrome and other genetic conditions
Uterine and outflow causes:
- Scarring of the womb lining (Asherman's syndrome) after surgery or infection
- Absent womb or vagina from birth (for example MRKH syndrome)
- Imperforate hymen or vaginal septum
Other causes: thyroid disease, Cushing's syndrome, congenital adrenal hyperplasia, and medicines such as some antipsychotics, hormonal contraceptives and chemotherapy.
How it develops (pathophysiology)
Normal menstrual cycle
Periods depend on a chain of hormone signals called the hypothalamic-pituitary-ovarian axis:
- The hypothalamus releases gonadotropin-releasing hormone (GnRH) in regular pulses.
- GnRH stimulates the pituitary gland to release follicle-stimulating hormone (FSH) and luteinising hormone (LH).
- FSH stimulates follicles in the ovaries to grow and make oestrogen, which thickens the womb lining.
- A surge of LH triggers ovulation. The empty follicle becomes the corpus luteum, which makes progesterone, preparing the lining for pregnancy.
- If pregnancy does not occur, progesterone falls and the lining sheds as a period.
A period also requires a healthy womb lining and an open outflow tract.
What goes wrong
Amenorrhoea occurs when any link in this chain fails:
- Hypothalamic amenorrhoea: energy shortage from low weight, excessive exercise or stress lowers leptin and raises cortisol, which suppresses GnRH pulses. FSH, LH and oestrogen fall, so follicles do not mature and the lining stays thin.
- Hyperprolactinaemia: high prolactin, from a prolactinoma or medicines that block dopamine, suppresses GnRH release.
- Pituitary damage reduces FSH and LH production.
- PCOS: high insulin and androgen levels disrupt follicle development, so ovulation fails. Oestrogen is usually present, but without ovulation there is no progesterone fall to trigger regular periods.
- Premature ovarian insufficiency: the ovaries run out of functioning follicles early, so oestrogen falls and FSH rises as the pituitary tries to stimulate them.
- Thyroid disease alters GnRH and prolactin and affects ovarian function.
- Uterine scarring prevents the lining from growing and shedding even when hormones are normal.
- Outflow obstruction means blood is produced but cannot leave, sometimes causing cyclical pain.
Why the symptoms and effects happen
- Absent periods result directly from the failure of the cycle.
- Hot flushes and vaginal dryness occur when oestrogen is low.
- Excess hair and acne reflect high androgens in PCOS.
- Milky nipple discharge results from high prolactin.
- Headaches and visual changes can occur with a large pituitary tumour.
- Bone thinning develops because oestrogen is needed to maintain bone density.
How treatment acts on the mechanism
Restoring energy balance (gaining weight, reducing training) allows GnRH pulses to resume. Dopamine agonists such as cabergoline lower prolactin and shrink prolactinomas. Hormone replacement provides oestrogen to protect bones and heart in hypothalamic amenorrhoea or ovarian insufficiency. In PCOS, weight loss, metformin and cyclical progestogens restore ovulation or shedding. Surgery corrects anatomical blockages or scarring.
Types
- Primary amenorrhoea: periods never started
- Secondary amenorrhoea: periods stopped after starting
- Classified by cause: hypothalamic, pituitary, ovarian, uterine or outflow tract
Signs and symptoms
- No periods
- Depending on the cause:
- Hot flushes, night sweats and vaginal dryness
- Excess facial or body hair, acne and weight gain
- Milky discharge from the nipples
- Headaches or problems with vision
- Cyclical lower abdominal pain without bleeding (outflow obstruction)
- Delayed breast development or growth in primary amenorrhoea
How it is diagnosed
- Pregnancy test, always first
- History of weight changes, exercise, stress, medicines and symptoms
- Examination, including weight, BMI and signs of high androgens
- Blood tests: FSH, LH, oestradiol, prolactin, thyroid function, testosterone
- Pelvic ultrasound to look at the ovaries and womb
- MRI of the pituitary if prolactin is high or there are visual symptoms
- Karyotype (chromosome test) in primary amenorrhoea or premature ovarian insufficiency
- Progestogen challenge occasionally
Possible complications
- Infertility
- Osteoporosis and fractures
- Increased cardiovascular risk with long-term low oestrogen
- Endometrial hyperplasia in conditions with unopposed oestrogen, such as PCOS
- Psychological distress
Goals of treatment
Treatment aims to identify and treat the cause, restore periods or fertility where wanted, and protect bone and heart health.
Medicines
- Cabergoline or bromocriptine for high prolactin
- Hormone replacement therapy or the combined pill for low oestrogen
- Cyclical progestogens to protect the womb lining in PCOS
- Metformin in some women with PCOS
- Fertility treatments such as ovulation induction
- Thyroid treatment where relevant
- Calcium and vitamin D for bone health
Other treatments
- Nutritional support and weight restoration
- Adjusting training intensity
- Treatment for eating disorders
- Stress management and psychological support
- Surgery for uterine scarring, outflow blockages or some pituitary tumours
Living with it and prevention
- Maintain a healthy weight and balanced diet
- Balance exercise with adequate nutrition
- Manage stress
- Seek help early if periods stop
Monitoring and follow-up
Follow-up checks that periods return and monitors bone density in long-term low oestrogen. Women with PCOS are monitored for diabetes and cardiovascular risk.
Outlook
The outlook depends on the cause. Many causes are treatable, and periods return once the cause is addressed. Premature ovarian insufficiency is usually permanent but managed with hormone replacement.
Special considerations
- Teenagers: delayed puberty needs assessment if periods have not started by 15
- Athletes: the female athlete triad (low energy, amenorrhoea, low bone density) needs attention
- Women wanting pregnancy: fertility specialists can help
