Amenorrhoea

Secondary amenorrhoea

Secondary amenorrhoea is commoner so it will be discussed first and in more detail.

There are two areas of the brain which influence the menstrual cycle – the hypothalamus and the pituitary. The hypothalamus produces gonadotrophin releasing hormone (GnRH) which stimulates the anterior pituitary to produce luteinising hormone (LH) and follicle stimulating hormone (FSH). The anterior pituitary hormones then affect the ovaries causing release of oestradiol, progesterone and inhibin. These hormones have a intricate link and the timings and amounts affect the menstrual cycle.

The diagram below illustrates the influence of the brain and ovaries on the production of hormones.

Hypothalamic causes

• The commonest reason for problems at this level is low weight or a low body mass index. If a woman’s weight is below 10-15 percent of her expected normal range it may be that the levels of GnRH are reduced and this can cause amenorrhoea.
• Excessive exercise may result in a low body mass index/weight, but there may be other factors.
• General health problems such as tuberculosis or sarcoidosis, which are rare, but can also affect menses at this level.
• Severe head injury or previous radiotherapy to the brain can cause decreased GnRH leading to amenorrhoea.
• Although rare, brain tumours, both benign and malignant, can cause amenorrhoea.

Pituitary causes

• Sometimes a tumour, usually benign, of the pituitary can cause high levels of prolactin which decrease GnRH production from the hypothalamus causing amenorrhoea.
• If a woman has experienced major haemorrhage, requiring intensive treatment and blood transfusions, usually at childbirth when the pituitary is larger and more sensitive, this can result in damage to the pituitary reducing the release of FSH and LH and causing amenorrhoea.

Ovarian causes

• Polycystic ovarian syndrome (PCOS) is one of the most common causes of amenorrhoea and is found in about 8 percent of the female population.
• Premature ovarian failure is defined as the stopping of menses prior to age 40, with high levels of FSH and LH. The cause in most women is not found but it can be a result of treatment with medication such as chemotherapy; radiotherapy; infection; autoimmune disease; or very rarely a chromosomal problem.
• Rarely, benign cysts of the ovaries, dermoid cysts can cause amenorrhoea.

Other causes

• Cervical stenosis, a blockage that occurs in the cervical canal, when the menses cannot flow out of the uterine cavity, may result in amenorrhoea. This can be caused by surgery.
• Ashermann’s syndrome which is caused by surgery or infection that results in scar tissue within the uterine cavity. This causes the endometrium, lining of the uterus, to not develop normally causing amenorrhoea.
• Drugs may influence the menses and these may be taken as part of the treatment for heavy menses e.g. progesterones or hormone replacement therapy or the combined pill if taken continuously. Other drugs such a medications for nausea can have side effects of stopping the normal menstrual cycle, but this is rare.
• Any chronic health problems may influence the menstrual cycle and cause amenorrhoea, e.g. diabetes, renal failure, thyroid disease, liver disease.
• Very rarely, tumours of the adrenal glands, a gland near the kidney can cause amenorrhoea.

Primary amenorrhoea

Again, the causes can be split into the various levels.

Commonly it can be constitutional, often following a family pattern, which is the commonest cause. However, it can also be due to the effect of other chronic illnesses such as diabetes.

Anorexia nervosa or excessive exercise can be a cause in teenagers. Problems with the development of the pituitary or tumours of the pituitary or hydrocephalus are much rarer causes.

Problems with the normal functioning of the ovaries or the absence of ovaries can also result in no menses. This can be due to abnormal development, premature ovarian failure, genetic problems, autoimmune disease, infections or following chemotherapy/ radiotherapy.

Genetic problems can be a rare cause of amenorrhoea e.g. Turner syndrome which is when the child only has one copy of the X chromosome.

Anatomical causes are more common in primary amenorrhoea:

• Imperforate hymen, which is a hymen with no opening which also usually presents with pain.
• Developmental abnormalities of the vagina, cervix and uterus such as a vaginal septum, or even absent uterus.