Your Girlfriend is in Town
Your body, and in particular your uterus and ovaries are your best friend. It is a love/hate relationship that you need to know. Girlfriends do not always see eye to eye on everything, so appreciate how sometimes she may not cooperate. She may arrive early or unexpectedly when you have just gotten out of the shower, when you are in the middle of a work day, or when you decided to wear those fabulous white pants that look so hot on you. Sometimes, she trots in with other friends (aka acne, painful breasts, and bloating). If you understand what makes her tick, you will be fabulous friends for life.
The most important thing for you to understand about your body is the basic menstrual cycle. It is the amazing cream of the crop of physiology. It is complex, driven by many different hormones in precise patterns, that, if any are out of synchronization, the system will not work. Keep an eye on the chart and follow along. When the hormones are mentioned, refer back to it, and reread it. Getting this down now will enhance your ability to understand the other topics and not leave you feeling like you need to flip back constantly.
The chart reads left to right, with the beginning of your cycle at the left. The synchrony of events happens vertically. To be precise, all of the events lining up vertically are happening at the same time. Look at the days of the cycle on the bottom of the chart and note that the first day is ‘Day 1’. Also, Day 1 represents the first day of your period. This chart represents an average cycle of twenty eight days. It is normal for cycles to vary from twenty four to thirty five days in the majority of women. A few women have longer time frames between periods while others experience shorter ones. This is fine, since we are not all the same. A common misconception is that the cycle ends with menstruation. Understanding that this event comes first is important as you will see time and again in the coming chapters.
You are born with all of the eggs you will ever have, which is about twenty million. That seems ludicrous to me because the average male has double that number of sperm in each ejaculation. Men also seem to have that never-ending supply of swimmers. Back on base, these “birth right” eggs are only partially developed. Puberty triggers the final development of them. One at a time, as directed by the brain, each egg will be hormonally driven to develop and ovulate. They are also called follicles.
The menstrual cycle is broken into two main phases. You might hear at your doctor’s office the words follicular phase and luteal phase. Follicular phase refers to the development of the follicle/egg before ovulation of it, while the luteal phase is the development of the corpus luteum after ovulation of the follicle/egg (described below).
Four hormones are seen on the graph. Lutenizing Hormone (now will be referred to as LH) and Follicle Stimulating Hormone (now will be referred to as FSH) are made in the brain and they tell the ovary what to do. The two main hormones produced by the ovary areestrogen and progesterone. Estrogen and progesterone control the growth of the lining of the uterus. In general, estrogen thickens the lining of the uterus, while progesterone prepares the lining to shed off.
The female body operates on hormone signals. Each organ or part of your body will make a hormone to tell the other part what it is “thinking”. Basic communication is essential and the SIGNALS are very well defined.
Let’s look again. In the beginning of the cycle, the lining is shedding off because there are no hormones to stabilize it. The estrogen is low and progesterone is low in the body. The brain hormones (LH and FSH) are low also. This is the FIRST SIGNAL to the brain. When this “void” or lack of hormones from the ovaries is detected by the brain, your brain begins to make LH again. LH tells the ovaries to start making a new egg, or “follicle”. (The words egg and follicle are interchangeable.) See how the egg starts small, and as days go by, it gets larger. As it gets larger, it secretes estrogen. Watch the graph showing your estrogen level in your blood go up as the egg grows. Subsequently, estrogen will cause the uterus lining to thicken. As the egg approaches its maturity, or optimal size, it will produce a high enough estrogen level to set the SECOND SIGNAL into motion.
The second signal is complex. Two things happen in the second signal. The estrogen must 1) peak and2) the brain must respond to it. There is a certain attainable blood estrogen level at which the brain will then respond by producing a surge of LH and FSH. It is like mama bear’s bed. It needs to be just right. Note that the peak in estrogen precedes the peaks of LH and FSH. This subsequent peak in LH and FSH alters the follicle and tells it to release the egg inside.
The release of the egg happens approximately fourteen to fifteen days after the firstday of your period. Therefore, these are your most fertile days. If you are hankering to be pregnant, you would want to have the most frequent sex around these days. If not, then run the other way. After ovulation, the egg has finished developing, and the estrogen level is never that high again during the rest of your cycle. It begins to slowly decline.
Now that the egg is released, the “casing”, or shell that the egg was in, which remains in the ovary, is still of prime importance. Now it is called the corpus luteum and it primarily makes progesterone. The body now enters the luteal phase. Progesterone alters the blood vessels in the lining of the uterus. When it declines in your blood as shown in the second half of the graph, the lining of the uterus will shed.
Nearing day twenty seven and twenty eight, the estrogen and progesterone levels drop, as do the levels of LH and FSH. The lining has no hormone support, and it sheds: your girlfriend has arrived. Hormone levels remain low for several days. The brain senses the low hormones levels, and the cycle starts all over again.
To summarize in all of this pomp and circumstance: Brain tells ovary to make egg. Egg makes estrogen. Estrogen thickens lining of uterus. Brain tells ovary to release egg. Estrogen goes down. Corpus luteum makes progesterone. Progesterone gets lining of uterus ready to shed. Lining sheds. Voila! Let’s go have a cocktail.
Allyn G. Schaub M.D.
Your Girlfriend GynecologistTM