Menopause

Menopause is the physiological cessation of menstrual cycles associated with advancing age in species that experience such cycles. Menopause is sometimes referred to as change of life or climacteric.

Overview
Menopause occurs as the ovaries stop producing estrogen, causing the reproductive system to gradually shut down. As the body adapts to the changing levels of natural hormones, vasomotor symptoms such as hot flashes and palpitations, psychological symptoms such as increased depression, anxiety, irritability, mood swings and lack of concentration, and atrophic symptoms such as vaginal dryness and urgency of urination appear. Together with these symptoms, the woman may also have increasingly scanty and erratic menstrual periods.

Technically, menopause refers to the cessation of menses; whereas the gradual process through which this occurs, which typically takes a year but may last as little as six months or more than five years, is known as climacteric. Popular use, however, replaces climacteric with menopause. A natural or physiological menopause is that which occurs as a part of a woman's normal aging process. However, menopause can be surgically induced by such procedures as hysterectomy (when this procedure includes oophorectomy, removal of the ovaries).

The average onset of menopause is 50.5 years, but some women enter menopause at a younger age, especially if they have suffered from cancer or another serious illness and undergone chemotherapy. Premature menopause (or premature ovarian failure) is defined as menopause occurring before the age of 40, and occurs in one percent of women. Other causes of premature menopause include autoimmune disorders, thyroid disease, and diabetes mellitus. Premature menopause is diagnosed by measuring the levels of follicle stimulating hormone (FSH) and luteinizing hormone (LH); the levels of these hormones will be higher if menopause has occurred. Rates of premature menopause have been found to be significantly higher in both fraternal and identical twins; approximately five percent of twins reach menopause before the age of 40. The reasons for this are not completely understood. Transplants of ovarian tissue between identical twins have been successful in restoring fertility.

Post-menopausal women, especially Caucasian women of European descent, are at increased risk of osteoporosis.

Animals other than human beings rarely experience menopause, possibly because they simply do not live long enough to reach it (see Grandmother hypothesis). However, recent studies have shown menopause in gorillas, with an average age of 44 at onset.

Perimenopause
Perimenopause refers to the time preceding menopause, during which the production of hormones such as estrogen and progesterone diminishes and becomes more irregular. During this period fertility diminishes. Menopause is arbitrarily defined as a minimum of twelve months without menstruation. Perimenopause can begin as early as age 35, although it usually begins much later. It can last for a few months or for several years. The duration of perimenopause cannot be predicted in advance.

Etiology
The cessation of menses is the result of the eventual atresia of almost all oocytes in the ovaries. This causes an increase in circulating FSH and LH levels as there are a decreased number of oocytes responding to these hormones and producing estrogen. This decrease in the production of estrogen leads to the post-menopausal symptoms of hot flashes, insomnia, osteoporosis, atherosclerosis, vaginal atrophy and depression.

Cigarette smoking has been found to decrease the age at menopause by as much as one year however, premature menopause (before the age of 40) is generally idiopathic.

Symptoms
The clinical features of menopause are caused by the estrogen deficiency. Vasomotor instability
 * hot flashes, hot flushes
 * sleep disturbances

Urogenital atrophy Skeletal Skin, soft tissue Psychological
 * dyspareunia
 * itching
 * dryness
 * bleeding
 * urinary frequency
 * urinary urgency
 * urinary incontinence
 * osteoporosis
 * joint, muscle pain
 * back pain
 * breast atrophy
 * skin thinning
 * decreased elasticity
 * mood disturbance
 * irritability
 * fatigue
 * decreased libido
 * memory loss

Treatment of symptoms
Medical treatments for menopausal symptoms have been developed. Most notably, Hormone Replacement Therapy (HRT), has been used to reduce the weakening of bones (known as osteoporosis). However, some women have resisted the implication that menopause is a disorder, seeing it as a natural stage of life. There has also been scientific controversy over whether the benefits of HRT outweigh the risks. For many years, women were advised to take hormone therapy after menopause to reduce their risk of heart disease and various aspects of aging. However, a large, randomized, controlled trial (the Women's Health Initiative) found that women undergoing HRT had an increased risk of Alzheimer's disease, breast cancer, heart disease and stroke.