Menopause transition: A woman can usually tell if she is approaching menopause because her menstrual periods starts changing. The medical terms used to describe this time are the "menopause transition" and "perimenopause".
The changes of the menopause transition (perimenopause) typically begin several years before the natural menopause. Menopause transition is a time when the levels of hormones produced by the aging ovaries fluctuate, leading to irregular menstrual patterns (irregularity in the length of the period, the time between periods, and the level of flow) and hot flashes (a sudden warm feeling with flushing). Other changes that may be associated with the perimenopause and menopause include night sweats, mood swings, vaginal dryness, fluctuations in sexual desire (libido), forgetfulness, trouble sleeping, and fatigue, probably from loss of sleep.
The menopause is the "change of life," the time in a woman's life when menstrual periods permanently stop. Menopause is the opposite of the menarche. Menopause is defined as the time when there have been no menstrual periods for 12 consecutive months and no other biological or physiological cause can be identified. It is the end of fertility, the end of the childbearing years. (A woman may still, however, be able to become pregnant unless 12 consecutive months have passed without a period.)
Natural menopause occurs when the ovaries naturally begin decreasing their production of the sex hormones estrogen and progesterone.
Induced menopause occurs if the ovaries are surgically removed (by bilateral oophorectomy) or damaged by radiation or drugs. Due to the abrupt cutoff of ovarian hormones, induced menopause causes the sudden onset of hot flashes and other menopause-related symptoms such as vaginal dryness and a decline in sex drive.
The timing of natural menopause is variable. In the western world the average age is now 51. There is no relation between the time of a woman's first period and her age at menopause. The age at menopause is not influenced by a woman's race, height, number of children or use of oral contraceptives.