Primary amenorrhoea refers to the failure to establish menstruation by 16 years of age, in those with normal secondary sexual characteristics, or by 14 years of age in those with no secondary sexual characteristics.

For girls without secondary characteristics causes include Turners syndrome or hypothalamic-pituitary dysfunction. For girls with signs of secondary sexual characteristics, the cause is more likely to be androgen insensitivity syndrome or a genito-urinary malformation. Most girls with primary amenorrhoea will be referred to local gynaecology service or a regional specialist Paediatric and Adolescent Gynaecology clinic.

The average age of the first menstruation, known as ‘menarche’, is 12 years old and 95 per cent of girls will have started menstruating by the age of 15 years.

Secondary amenorrhoea occurs in approximately 3% of women and refers to the cessation of previously established menstruation for 3 cycles or for 6 or more months.

Causes include:

• pregnancy
• low body mass index
• polycystic ovarian syndrome
• premature ovarian insufficiency
• hypothalamic amenorrhoea
• hyperprolactinaemia.

It should be noted that women who have amenorrhoea are at a greater risk of endometrial hyperplasia. This is an overgrowth of the endometrial cells causing a thickening of the lining of the womb. It is advisable that women have two to three withdrawal bleeds a year following short courses of progesterone to prevent abnormal thickening of the endometrium.

Investigations include:

• pregnancy test
• weight and height
• physical examination
• blood tests including hormonal profile (FSH, LH, oestradiol)
• thyroid function
• prolactin
• androgen concentration.

For secondary amenorrhoea, treatment will depend on the diagnosis. If a woman is concerned about her fertility then a referral to secondary care should be discussed.

Further resources

• RCN: Women’s Health Pocket Guides - Amenorrhoea page 20 
• British Society of Paediatric and Adolescent Gynaecology 
• Clinical Knowledge Summaries: Amenorrhoea