The causes of menopause can be considered from complementary proximate (mechanistic) and ultimate (adaptive evolutionary) perspectives.
Proximate perspective
Natural or physiological menopause occurs as a part of a woman's normal aging process. It is the result of the eventual atresia of almost all oocytes in the ovaries, causing an increase in circulating follicle stimulating hormone (FSH) and luteinizing hormone (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 perimenopausal symptoms of hot flashes, insomnia and mood changes. Long term effects may include osteoporosis and vaginal atrophy.
Menopause can be surgically induced by bilateral oophorectomy (removal of ovaries), which is often, but not always, done in conjunction with removal of the Fallopian tubes (salpingo-oophorectomy) and uterus (hysterectomy). Cessation of menses as a result of removal of the ovaries is called "surgical menopause". The sudden and complete drop in hormone levels usually produces extreme withdrawal symptoms such as hot flashes, etc. Removal of the uterus, hysterectomy, does not cause menopause, although pelvic surgery can often precipitate a somewhat earlier menopause, perhaps because of a compromised blood supply to the ovaries.
Cigarette smoking has been found to decrease the age of physiological menopause by as much as one year, and women who have undergone hysterectomy with ovary conservation go through menopause 3.7 years earlier than average. However, premature menopause (before the age of 40) is generally idiopathic.
Further Reading
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