Defining Womanhood–The Menstrual Cycle

Each month a woman experiences a menstrual cycle. That means for the average woman who menstruates for 40 years, she has 500 periods over her lifetime. The cyclical process of menstruation is a delicate and complex one–it’s no wonder women experience so many physical and emotional changes throughout the month. You might find you feel really good one week a month. The rest of the month you may experience changes similar to the Dow Jones: Up-and-down-and-up-and-down.

If one segment of your hormonal process is off, your entire cycle may suffer. Often you don’t even realize why you’re feeling tired, or in pain, or suffering unusual menstrual or ovulatory symptoms. During your menstrual cycle, estrogen, progesterone, and other hormones are continuously on the move. Your well-being depends on a proper balance between estrogen and progesterone, as well as appropriate levels of FSH and LH. Once I understood these changes, I was able to identify that my hormonal problems were manifesting as PMS. Let me explain it to you.

Your body prepares and expects a baby every month of your menstruating years. It does this by lining your uterus with a rich, spongy bed of blood vessels, glands, and cells–not unlike a soft cuddly crib. When that doesn’t happen, menstruation cleans out the uterus and tries again. While the uterine crib is being made-up, your ovaries harvest several eggs and then pop out the best one. If your egg doesn’t meet a sperm, your womb sheds its lining–strips the bed so to speak–and starts anew.

The day you begin to bleed is day one of your cycle, which averages 28 days (although most women have normal cycles ranging from 20 to 40 days).

A simple way of visualizing how your hormonal process works and how that correlates with the journey of the egg is to divide your cycle into four phases

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1: The four phases of your menstrual cycle.

Phase 1: Menstruation

Days 1-5: Menstruation occurs, estrogen levels are low and then begin to rise. The pituitary secretes FSH.

Phase 2: The follicular or estrogenic phase

Days 6-8: Estrogen levels continue to rise, the egg-producing follicle grows.

Days 9-12: Fertile-type mucous is produced by the cervix to help sperm find the egg. Pituitary begins secreting LH.

Phase 3: Ovulation

Days 13-16: Ovulation occurs and LH begins to fall. Estrogen peaks and then decreases slightly. High estrogen levels turn FSH off. Basal body temperature dips then rise.

Phase 4: The luteal or progesterone phase

Days 17-20: Progesterone begins to rise. Estrogen rises again slightly. The egg travels toward the uterus.

Days 21-24: Estrogen and progesterone levels peak then begin to fall.

FSH and LH also on the decline.

Days 25-28: Body prepares to eliminate uterine lining–menstruation.

2: The hormonal feedback mechanism during a menstrual cycle.

menstrual cycle hormones

Hypothalamus secretes:

1)         Follicle stimulating hormone-releasing factor (FSH-RF).

2)         Luteinizing hormone-releasing factor (LH-RF).

Pituitary secretes:

1)         Follicle stimulating hormone (FSH).

2)         Luteinizing hormone (LH).

Ovaries

1)         FSH stimulates the development of follicles.

2)         Follicle secretes estrogen.

3)         LH stimulates ovulation.

4)         Corpus luteum (left after follicle releases egg) secretes progesterone.

Uterus

1)         Estrogen stimulates a spongy bed-like endometrium to form inside the uterus during the first half of cycle.

2)         Progesterone maintains uterine lining during the second half of the cycle.

It’s your hypothalamus, the queen bee of the endocrine system, that kicks menstruation, the first phase, into gear. With messengers called follicle-stimulating hormone-releasing factor (FSH-RF) and luteinizing hormone-releasing factor (LH-RF), the hypothalamus notifies the pituitary, the middle manager in female reproduction, to make its own hormones–follicle stimulating hormone (FSH) and luteinizing hormone (LH). These pituitary hormones are easy to remember because their names describe exactly what they do. FSH stimulates the follicles or pre-egg pouches in your ovaries. LH forms luteal tissue, that is the corpus luteum or remains of the mature egg follicle.

Once you stop bleeding (around day 5 or 6–everyone is different) then the follicular or estrogenic phase starts. As you can see, each phase is named according to what hormone (in this case estrogen) or event (follicle maturation) dominates. Your pituitary sends FSH down to your ovaries so the follicles in your ovaries can grow up and become eggs.

Each one of us is born with as many as 400,000 follicles that last for life. This is unlike men who produce a fresh batch of sperm every few months until they die. Not all of these follicles get a chance at the big time, namely ovulation. Some mature, but then dissolve. Others merely deteriorate with age. But as I’ll explain later, when your follicles run out, then menopause is just over the hill.

It’s the maturing follicle within your ovary that secretes estrogen and gets the spongy uterine lining called the endometrium ready–the crib for the fetus we mentioned earlier. I like to think of estrogen as the maid of the reproductive system. She’s there during the first half of your cycle, bustling around getting the nursery set for a fertilized egg. (Of course, estrogen has other effects on your body, but we’re concentrating on the menstrual cycle right now.) Estrogen continues to rise during this time and then peaks. When estrogen levels are high enough, FSH secretion is turned off and your pituitary sends out LH instead–around day 10.

LH causes ovulation, the release of an egg from one of your ovaries; your ovaries usually take turns ovulating every other month. Ovulation occurs at the midpoint or third phase of your cycle, usually around day 14. Once it escapes from the ovary, your egg begins its journey down the fallopian tube where it will be fertilized if the sperm reaches it. This is called conception. You might feel a slight twinge or mild crampy sensation in your abdomen during ovulation. Doctors call this mittelschmerz which literally means “middle pain” in German. Some women feel nothing.

If you practice natural family planning and chart your basal body temperature (BBT) upon waking every morning, you may notice a dip in temperature the day before ovulation, and a rise of about 4/10 of a degree Fahrenheit the day after ovulation, caused by an upward surge of progesterone. However, the temperature can increase a day or two before ovulation too. This is why you can’t depend on BBT as a reliable form of birth control. This temperature remains elevated if you are pregnant, and will drop just before menstruation begins if you’re not.

The luteal phase begins the second half of your cycle (and fourth phase). Once the egg has left your ovary, the pituitary begins to secrete increased quantities of luteotropic hormone (LTH). LTH acts on the egg’s remains left in your ovary (called the ruptured egg follicle) and converts it into the corpus luteum. The corpus luteum, Latin for yellow body, begins to produce more progesterone and slightly less estrogen. Progesterone is like a nanny who keeps your uterus spongy and ready for baby to appear.

Even though estrogen is the boss during the first half of your cycle, and progesterone during the second, it’s not an all-or-nothing situation. Estrogen levels are still relatively high after ovulation. In fact, both of these hormones are vital to keeping a pregnancy going. Estrogen takes care of your womb by enhancing uterine muscles, making sure there’s lots of blood and preparing your breasts for nursing. Progesterone, on the other hand, relaxes your womb so you don’t go into labor prematurely. It also calms your bowels and stomach so you absorb more nutrients, important for a growing fetus.

As I’ve said before, these two hormones work in opposite but cooperative ways. It’s like the perfect partnership where each member knows her place and picks up where the other leaves off.

These higher progesterone levels inhibit pituitary production of LTH. As LTH falls off, the corpus luteum breaks down. Without sufficient amounts of progesterone to maintain the uterine lining, the corpus luteum (now called corpus albicans or white body) dries up and stops making hormones. The egg joins the soon-to-be menstrual fluids in your uterus. Then, your menstrual cycle occurs all over again.