Causes of Menopause

By Menopause Now Editorial Team | Updated: Jul 18, 2019


Menopause is a natural phase in every woman's life, which occurs due to aging as the ovaries run out of their egg supply, stop hormonal production, and halt reproductive functions.

In some cases, however, a woman's health conditions force her to enter induced menopause sooner, most commonly through surgery or medications, in order to stop the disease from progressing and reduce the symptoms.

Continue reading to discover what causes menopause, including natural and induced causes, to have a better understanding of the changes taking place in your body.

Natural Causes of Menopause

The main underlying cause of natural menopause is hormonal imbalance.

While there are numerous physiological changes that begin long before a woman reaches menopause, the entire menopausal transition revolves around two major processes: the loss of ovarian follicles and the resulting decrease in estrogen production.

Loss of Ovarian Follicles

Women are born with all the eggs they will ever have, about 1-2 million at birth, all contained in sacs called follicles. This lifetime supply, referred to as an ovarian reserve, undergoes a gradual decline at various rates from birth through all the reproductive phases.

This natural decline happens as the ovaries mature hundreds of eggs each menstrual cycle with only one being released on ovulation day. Unused eggs are being lost, thus reducing the total ovarian supply.

After the age of 35, the egg loss becomes steeper and will continue accelerating into a woman's 40s and throughout perimenopause until the ovarian reserve reaches a total depletion around the age of 51, marking the end of a woman's reproductive abilities.

Decreased Estrogen Production

As the ovaries slow down their egg release, the production of reproductive hormones fluctuates drastically throughout the menopausal transition until eventually settling at permanently low levels in postmenopause.

This hormonal imbalance occurs because the ovaries are the main producers of estrogen and progesterone, key hormones responsible for orchestrating the entire menstrual cycle and vital to fertility. Without ovarian eggs, the hormonal cascade cannot continue.

In a woman's early to mid-40s, a low egg supply and hormonal shifts bring about irregular periods among other menopause symptoms, such as night sweats or mood swings. Eventually, the ovaries cease their monthly egg release and, consequently, hormonal production. As such, when a menstrual cycle does not occur for 12 months in a row, a woman is said to have reached natural menopause.

Induced Causes of Menopause

Menopause can also occur as a result of surgical intervention or medical treatment, in which case it is referred to as induced menopause.

Like natural causes of menopause, surgical or medical menopause also triggers hormonal imbalance as a woman's fertility comes to an end, but the hormonal shifts occur more abruptly.

Surgical Menopause

Surgical menopause occurs when both ovaries are removed, a procedure called bilateral oophorectomy. It is performed on women with cancer of the reproductive organs as well as symptomatic ovarian cysts, fibroids, ovary torsion, or endometriosis. Surgical menopause is permanent.

The removal of the ovaries (the main estrogen producers) triggers a drastic decrease in hormone levels, which tends to brings about more severe menopause symptoms, like hot flashes, vaginal dryness, or loss of libido, than with natural menopause.

Oophorectomy can be performed with or without a hysterectomy, the removal of the uterus. However, hysterectomy alone with the ovaries left intact does not trigger an immediate menopause. Yet, women normally enter postmenopause sooner, usually within five years after the surgery.

Medical Menopause

Medical menopause is caused by medical treatments that damage or shut down the ovaries, thus suppressing their hormonal production either temporarily or permanently.

There are two possible causes of medically induced menopause: chemotherapy or radiation therapy, both of which are used to treat cancer or certain autoimmune diseases. In some cases, temporary ovarian suppression is necessary to halt estrogen production and starve the cancer cells.

Because these treatments do not affect all women alike, it is difficult to precisely determine their effects on their reproductive health. As such, the resulting menopause symptoms might be delayed or appear immediately and may be reversible or permanent. Younger women tend to regain their ovarian functions sometime after treatment is completed, while in middle-aged women, medically-induced menopause is more likely to be irreversible.

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