Menopause, natural: Natural menopause occurs when the ovaries naturally decrease their production of the sex hormones estrogen and progesterone; there are no menstrual periods for 12 consecutive months; and no other biological or physiological cause can account for this.
Natural menopause is as opposed to induced menopause. Induced menopause occurs when the ovaries are surgically removed (by bilateral oophorectomy) or are 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 a vaginal dryness and a decline in sex drive.
A woman can usually tell if she is approaching menopause because her menstrual periods start changing. The medical terms used to describe this time are the "menopause transition" and "perimenopause". The changes of the menopause transition (perimenopause) begin several years before the natural menopause 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 blushing).
Other changes associated with the menopause (natural or induced) include night sweats, mood swings, vaginal dryness, fluctuations in sexual desire (libido), forgetfulness, trouble sleeping and fatigue, probably from loss of sleep. 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.