Normal Menopause – what happens actually?

Understanding your normal physiology

There are numerous popular fads regarding menopause. Some, like getting a tubal reversal after 5 years of tubal ligation can induce menopause, are absurd, while others, such as hot flashes, are certainly true. In order to understand this and pick the truths from the myths, you need to go a bit deeper into the physiology of normal menopause.

An oocyte is an immature cell in the ovary.  A primary oocyte is formed in the ovaries of a woman before her birth. It becomes a secondary oocyte after the onset of menarche (the first menstrual period). This oocyte then becomes an ovum, which is released from the ovary during ovulation and perhaps fertilized by a sperm to form a zygote (a future embryo which then develops into a fetus).

When a female child is born, there are up to 100,000 oocytes in her ovary. Only about 400 are used in her reproductive life. Normal menopause occurs when these oocytes become depleted or non-functional.

A typical menstrual cycle occurs in fixed phases under the effect of various hormones. The following is a simple summary of a menstrual cycle.

A Regular Menstrual Cycle

Follicle Stimulating Hormone FSH and Luteinizing Hormone LH are secreted by the anterior pituitary gland. They are both released under the effect of gonadotropin releasing hormone (GnRH). This GnRH is released by the effect of Estrogen, ovulationyet another hormone. This estrogen is released by a mature follicle during the follicular phase. This follicle contains a primary oocyte. When the size of a follicle is big enough, the estrogen triggers a sudden release of LH. LH in turn helps in maturation of the oocyte into secondary oocyte and finally ovum, and it is released from the follicle in the ovary during ovulation. The empty follicle left behind is now called a corpus luteum.  This does not get destroyed right away but persists for some time in the ovary, releasing progesterone.  The progesterone makes a uterus receptive for an embryo to be implanted. This corpus luteum also releases inhibin, which inhibits or suppresses the release of FSH and LH temporarily. The unfertilized egg must then travel through the fallopian tube to reach a sperm coming through the tube from the uterus. (A tubal ligation would prevent this meeting of the egg and the sperm, and a tubal reversal could repair the ligated tube so that the egg and sperm could meet again). If they meet, and fertilization then occurs, the embryo is implanted in the uterus and forms a placenta. The placenta releases hCG which causes the corpus luteum to continue to release progesterone. In case of no fertilization, this corpus is reabsorbed and disappears in most cases. As there is no progesterone now, the mucosal lining of uterus gets destroyed, initiating menstrual bleeding. The effect of inhibin is lifted from FSH and LH, and the increase in FSH causes formation of more follicles to start the process again. Only one follicle matures to become the dominant follicle, the future corpus luteum, holding the primary oocyte.

So this was a normal menstrual cycle, when is normal menopause?

A primary follicle produces estrogen. With age, the oocytes become non-functional. As a result there are fewer primary follicles, reducing the levels of estrogen in the body. Without estrogen there will be no LH surge and no ovulation. No ovulation means no progesterone. That means general thinning of uterine mucosa, vaginal atrophy, and erratic menstruation. Furthermore, the perimenopausal symptoms that you experience i.e. insomnia, irascibility and headaches are due to the lack of estrogen. Post-menopausal urogenital symptoms and osteoporosis are also due to this low level of estrogen. Hormone replacement therapy is often prescribed to cut down the incidence of such symptoms.

Can menopause be induced?

Yes, a hysterectomy can induce menopause if the ovaries are also removed. It will then be called surgically induced menopause.

Will any surgery performed on my uterus induce menopause?

No. Except for removing the ovaries, or some brain surgeries, there are no other surgical procedures that will induce menopause. Neither tubal ligation nor tubal reversal has any effect on menopause.

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