Because of this, measurements of these hormones are not considered to be reliable guides to a womans exact menopausal status.Menopause occurs because of the sharp decrease of estradiol and progesterone production by the ovaries. After menopause, estrogen continues to be produced mostly by aromatase in fat tissues and is produced in small amounts in many other tissues such as ovaries, bone, blood vessels, and the brain where it acts locally. The substantial fall in circulating estradiol levels at menopause impacts many tissues, from brain to skin. In contrast to the sudden fall in estradiol during menopause, the levels of total and free testosterone, as well as dehydroepiandrosterone sulfate (DHEAS) and androstenedione appear to decline more or less steadily with age. An effect of natural menopause on circulating androgen levels has not been observed. Thus specific tissue effects of natural menopause cannot be attributed to loss of androgenic hormone production.Hot flashes and other vasomotor and body symptoms accompanying the menopausal transition are associated with estrogen insufficiency and changes that occur in the brain, primarily the hypothalamus and involve complex interplay between the neurotransmitters kisspeptin, neurokinin 3B (NK3B) and dynorphin, which are found in ‘KNDy’ neurons in the infundibular nucleus.Long-term effects of menopause may include osteoporosis, vaginal atrophy as well as changed metabolic profile resulting in increased cardiac and metabolic disease (diabetes) risks. Ovarian aging
Decreased inhibin feedback after hysterectomy is hypothesized to contribute to increased ovarian stimulation and earlier menopause. Hastened ovarian aging has been observed after endometrial ablation.
However, in about 50–80% of cases of premature ovarian insufficiency, the cause is unknown, i.e., it is generally idiopathic.An early menopause can be related to cigarette smoking, higher body mass index, racial and ethnic factors, illnesses, and the removal of the uterus.Rates of premature menopause have been found to be significantly higher in fraternal and identical twins; approximately 5% 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. Surgical menopause
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". Surgical treatments, such as the removal of ovaries, might cause periods to stop altogether. The sudden and complete drop in hormone levels may produce extreme withdrawal symptoms such as hot flashes, etc. The symptoms of early menopause may be more severe.Removal of the uterus without removal of the ovaries does not directly cause menopause, although pelvic surgery of this type can often precipitate a somewhat earlier menopause, perhaps because of a compromised blood supply to the ovaries. The time between surgery and possible early menopause is due to the fact that ovaries are still producing hormones. Mechanism
The menopausal transition, and postmenopause itself, is a natural change, not usually a disease state or a disorder.