The menopause is the biological stage in a woman’s life when menstruation permanently ceases. It marks the end of the female reproductive life. It occurs with the final menstrual period and is usually diagnosed clinically after 12 months of amenorrhoea. In the UK, the mean age of natural menopause is 51 years, although this can vary between different ethnic groups.
It is a physiological process that begins as perimenopause at around the age of 45, which is the period before menopause when the endocrinological, biological, and clinical features of approaching menopause commence.
Definitions
The menopause is defined as having occurred when a woman has had amenorrhoea (absent menstruation) for 12 months.
Premature menopause (also referred to as early menopause) is defined as when there has been amenorrhoea for 12 months in a woman under the age of 45.
Hormonal changes during the menopause
During the menopause, there is a decline in the sensitivity of the ovary to circulating gonadotropins (FSH and LH) due to a reduction in the number of binding sites due to the decrease in follicle numbers. This results in circulating oestrogen levels falling markedly due to decreased oestrogen secretion and an increase in anovulatory cycles.
Because of the low levels of circulating oestrogen, FSH and LH levels increase significantly. This eliminates the negative feedback on the hypothalamus and pituitary gland. The rise in FSH is further enhanced by a fall in the amount of inhibin released by developing follicles.
Clinical features of the menopause
These alterations in hormonal levels result in the appearance of menopausal symptoms and signs. These include the following:
- Irregular vaginal bleeding
- Vasomotor symptoms (hot flushes and night sweats)
- Urogenital changes (vaginal dryness, dyspareunia, urinary incontinence and urinary tract infections)
- Bone density changes
- Cardiovascular risk changes
- Sleep disturbance
- Mood changes
- Loss of libido
Approximately 80% of women undergoing menopause experience symptoms and around 25% are severely affected. Only a small proportion of menopausal women, however, require hormone replacement therapy (HRT). Symptoms may resolve in two to five years, but the median duration is seven years, and symptoms often last far longer than women anticipate.
Irregular vaginal bleeding
The majority of women notice menstrual irregularities during the menopause, which can last for as long as four years. The cycle may lengthen to many months or, conversely, shorten to two to three weeks. An increase in the amount of menstrual blood loss is also common. Around 10% of women have an abrupt cessation of periods.
Vaginal bleeding tends to become irregular as a result of menstruation from ovulatory cycles. Anovulatory cycles can also result in bleeding when the endometrium has proliferated without the balance of progesterone from the corpus luteum after ovulation. Excess oestrogen stimulates the undifferentiated proliferation of the endometrium. Progesterone, however, is required to provide structural support, and because it is present in insufficient levels to provide this support, the endometrial lining breaks down and sloughs at irregular intervals. This is referred to as breakthrough bleeding and can occur as often as every fortnight during the perimenopause. As levels of oestrogen decline further, both of these types of bleeding gradually cease.
Vasomotor symptoms
Vasomotor symptoms are the most commonly experienced menopausal symptoms, with approximately 75% of postmenopausal women experiencing hot flushes and night sweats and 25% of these being severely affected.
Hot flushes classically commence with red flushing of the face that spreads downward to the neck and chest. This is associated with a transient rise in body temperature. Why this occurs is not fully understood, but it is thought to be caused by a loss of homeostasis by the central thermoregulatory centre.
Urogenital changes
Urogenital changes occur due to a reduction in circulating oestrogen levels. There is pronounced atrophy of the vagina and vaginal walls and myometrial thinning. This can result in vaginal dryness, discomfort and dyspareunia.
The bladder and urethra share embryological derivation with the uterus and vagina, and so these tissues also atrophy with the decrease in circulating oestrogen. This can result in symptoms of urinary incontinence and an increased risk of developing urinary tract infections. Urinary symptoms may not manifest until 5-10 years after the menopause.
Bone density changes
Oestrogen is protective of bone mass and density via a reduction in osteoclast activity. With a decrease in circulating oestrogen levels, this bone mass protection is lost, which results in an acceleration of age-related loss of bone density and an increased frequency of fractures, most notably of the hip and wrist.
Cardiovascular risk changes
Oestrogen is also protective against cardiovascular disease. This is thought to occur via oestrogen, reducing levels of LDL cholesterol while raising HDL cholesterol. This protection is lost when circulating oestrogen levels fall, and after the menopause, women experience the same incidence of cardiovascular disease as men.
Sleep disturbance
Postmenopausal women commonly report sleep disturbance. This is thought to be primarily related to vasomotor symptoms occurring at night. Pyschosocial factors also play a role, and sleep deprivation can contribute to depression, irritability and poor concentration.
Mood changes
Mood changes are common around the menopause and can include anxiety, nervousness, irritability, memory loss and difficulty concentrating. Perimenopause is accompanied by an increased risk of new and recurrent depression.
There is some evidence that those women who have a history of premenstrual and postnatal depression have a higher risk of depression during their menopause.
Loss of libido
Loss of libido is also commonly reported by postmenopausal women. Several hormonal factors can contribute to this; oestrogen, progesterone and testosterone have all been implicated. Vaginal dryness, loss of self-image and other psychosocial factors also play a part.
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Thank you to the joint editorial team of www.mrcgpexamprep.co.uk for this article.
