Menopause

Here's something from Women'sHealth.gov

Menopause is the point in time when a woman's menstrual periods stop. Menopause happens because the ovaries stop producing the hormones estrogen and progesterone. Once you have gone through menopause, you can't get pregnant anymore. Some people call the years leading up to a woman's last period menopause, but that time actually is the menopausal transition, or perimenopause.

During the time of the menopausal transition (perimenopause), your periods can stop for a while and then start again. Therefore, the only way to know if you have gone through menopause is if you have not had your period for one year. (And it's not menopause if your periods stop for some other reason, like being sick.) The average age of menopause is 51, but for some women it happens as early as 40 or as late as 55.

After you go through menopause, you are considered in the post-menopausal stage of your life. Your female hormones won't go up and down the way they used to with your periods. They will stay at very low levels.

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Here's something from A.D.A.M. Medical Encyclopedia

Menopause is time in a woman's life when her periods (menstruation) eventually stop and the body goes through changes that no longer allow her to get pregnant. It is a natural event that normally occurs in women age 45 - 55.

Causes, incidence, and risk factors
During menopause, a woman's ovaries stop making eggs and they produce less estrogen and progesterone. Changes in these hormones cause menopause symptoms. Periods occur less often and eventually stop. Sometimes this happens suddenly. But most of the time, periods slowly stop over time.

Menopause is complete when you have not had a period for 1 year. This is called postmenopause. Women who are postmenopausal can no longer get pregnant.

Surgical menopause is when medical treatments cause a drop in estrogen. This can happen if your ovaries are removed or if you receive chemotherapy or hormone therapy for breast cancer.

Symptoms
Symptoms vary from woman to woman. They may last 5 or more years. Some women may have worse symptoms than others. Symptoms of surgical menopause can be more severe and start more suddenly.

The first thing you may notice is that your periods start to change. They might occur more often or less often. Some women might get their period every 3 weeks. This might last for 1 - 3 years before the periods completely stop.

Common symptoms of menopause include:
Menstrual periods that occur less often and eventually stop
Heart pounding or racing
Hot flashes, usually worst during the first 1 - 2 years
Night sweats
Skin flushing
Sleeping problems (insomnia)

Other symptoms of menopause may include:
Decreased interest in sex, possibly decreased response to sexual stimulation
Forgetfulness (in some women)
Headaches
Mood swings including irritability, depression, and anxiety
Urine leakage
Vaginal dryness and painful sexual intercourse
Vaginal infections
Joint aches and pains
Irregular heartbeat (palpitations)