The absence of menstruation for at least 3 months in women who would otherwise be having periods
There are two types of amenorrhoea: primary and secondary. If a girl has not started to menstruate by the age of 16, she is said to have primary amenorrhoea. Once menstruation has become established during puberty, it is normal for periods to stop during pregnancy, for a few months following childbirth, while breast-feeding, temporarily after ceasing to take oral contraceptive pills, and permanently at the menopause. If menstruation stops at any other time for at least 3 months, the condition is known as secondary amenorrhoea.
Amenorrhoea is often caused by a disturbance in the female sex hormones, which may be brought on by factors such as stress or depression. Excessive exercise and extreme or sudden weight loss (see Anorexia nervosa) may also lead to such hormonal disturbances and are common causes of amenorrhoea in athletes, gymnasts, and ballet dancers. Hormonal changes may lead to primary or secondary amenorrhoea, depending on when they occur.
Primary amenorrhoea is a characteristic feature of delayed puberty (see Abnormal puberty in females) and may be caused by a chromosomal abnormality. The failure of menstruation to start at puberty may also be due to a condition in which the hymen (the thin membrane over the vagina) has no opening, and menstrual blood cannot leave the body. In rare cases, the uterus is absent from birth, and therefore no menstruation can occur.
Secondary amenorrhoea may be due to a pituitary gland disorder, such as a pituitary tumour (see Prolactinoma). Some women have a premature menopause, in which periods cease before the age of 35. Other possible causes include disorders of the ovaries, such as polycystic ovary syndrome, and treatments such as radiotherapy and chemotherapy, which can result in damage to the ovaries.
Treatment is not needed if amenorrhoea lasts for only a few months after stopping oral contraceptive pills or occurs during pregnancy or breast-feeding. Menstruation normally resumes within a few months of giving birth if you are not breast-feeding or within a month of stopping breast-feeding. After the menopause, amenorrhoea will be permanent.
Amenorrhoea that occurs at any other time should be investigated. Your doctor will examine you and may perform a pregnancy test. You may also need to have blood tests to measure hormone levels, ultrasound scanning of the ovaries and uterus, and possibly CT scanning of the pituitary gland.
Treatment of the underlying disorder induces menstruation in most cases. If the cause cannot be treated, hormonal treatment may be used to start menstruation. If periods are absent due to stress, weight loss, or excessive exercise, they should occur if the problem is overcome.
From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.