What is a menstrual cycle?  We live through it month after month and yet for many women, the menstrual cycle is a complete mystery. It’s crazy how our menstrual cycle is a part of our life as a woman for so many years, and yet we know so little about it beyond the misery it can cause us!  I believe knowledge is power, and knowledge about how our bodies work gives us power to improve the way we feel, power to help our body work for us and power to get the help we need when something isn’t working right.  Let me walk you through your menstrual cycle and help you understand what is happening in your body at every stage.


The Four Phases of the Menstrual Cycle

Just as there are four seasons in the natural world, your female body has four phases in every menstrual cycle.  Each phase has distinct characteristics and specific hormonal fluctuations, and each phase is important to the cycle as a whole.  This cycle takes place over the course of anywhere from 21-35 days, and as you will see, your body choreographs an amazing hormonal dance every month!  Beginning to appreciate this is the beginning of period health.  Let’s look at each phase in detail now.

What is a menstrual cycle?


The Menstrual Phase

Usually we think of the menstrual phase as the end of your cycle, but really day 1 of your period is day 1 of your menstrual cycle.  At the start of your period, your sex hormones are at the lowest point of the entire cycle.  It might seem like everything related to your period happens from the waist down, but this is not true!  Your cycle is actually controlled by your brain.  More specifically, it is controlled by the hypothalamus and the pituitary gland.  It is during this bleeding phase that your hypothalamus releases gonadotropin-releasing hormone (GnRH), which signals your pituitary gland to produce follicle stimulating hormone (FSH).  The FSH then talks to your ovaries and prepares a handful of follicles, little sacs that each contain one egg, to get ready for ovulation.  Between days 5 and 7 of your cycle, one of the follicles from the group is chosen—this is the one that will be released at ovulation.  It’s important to know that it takes 100 days for your follicles to mature from dormancy to ovulation. If those follicles were unhealthy for any point of that 100 day journey, it could mean period problems months later.  Don’t be overwhelmed!  This just means that your menstrual health is an ongoing process, not a one-time thing!


The Follicular Phase

The follicles that were prepared during your menstrual phase now begin to produce estrogen, one of your body’s main sex hormones.   Your estrogen levels will continue to rise as this phase progresses and this estrogen is doing a number of things for your body.  First, it signals the body to reduce production of FSH and instead to start making luteinizing hormone (LH).  Even though it may not be your goal, your body’s goal every month is pregnancy, and estrogen prepares for this by thickening the uterine lining.  It also boosts neurotransmitters and provides benefits for your bones, muscles, brain, heart, sleep, skin and metabolism.


The Ovulatory Phase

The ovulatory phase is the shortest of all the phases, but probably the most important.  Ovulation is key to hormone health because ovulation is how your body makes progesterone. Without ovulation, half of your hormonal puzzle would be missing and the whole system would quickly get out of balance.  Estrogen levels continue to rise all the way up to ovulation and this tells the hypothalamus to trigger a surge of LH.  This surge in LH causes the follicle that was chosen earlier in the cycle to rupture and the egg to be released; this is ovulation.  Once the egg is released, it is moved into the fallopian tube where it will either be fertilized or begin to disintegrate.  The remainder of the follicle then becomes a temporary endocrine gland called the corpus luteum.

The Luteal Phase

After ovulation, FSH, LH and estrogen levels decline and progesterone takes over the show.  The corpus luteum’s main job is to produce progesterone for the remainder of your cycle, and the length of this half of your cycle depends on it’s ability to continue putting it out.  Your corpus luteum is seriously incredible. In less than a day it forms from almost nothing into a fully functional endocrine gland.  And the progesterone it makes it critical for your hormone health!  Progesterone is known as the keep calm and carry on hormone because it calms the nervous system and helps you deal with stress.  It also reduces inflammation, promotes sleep, and protects against heart disease and cancer.  Perhaps the biggest benefit of progesterone is the balance it brings to estrogen, like the yin to the yang.  Progesterone stays high throughout the luteal phase.  Estrogen drops sharply right after ovulation, but it rises one more time shortly before menstruation begins.  If the released egg is fertilized, it starts producing human chorionic gonadotropin hormone (hCG) and the miracle of pregnancy is begun.  If it was not fertilized, the corpus luteum function declines after 9-11 days and progesterone and estrogen drop.  This drop triggers menstruation to begin and the whole cycle starts again.

What’s the Takeaway?

Phew!  Are you still with me?  That was a lot of information, but I hope that what you take away from this is a general understanding of the hormonal fluctuations happening in your body every month as well as a little bit of awe at how incredible our female bodies are for pulling all of this off.  We’re pretty much all super-women!  Like I said earlier, knowledge is power and I hope this knowledge of how your cycle works empowers you to take charge of your health and feel less like the victim of your cycle every month.  Be sure to stay tuned to learn more about what’s normal and what’s not during your cycle, how to track your cycle, and how to harness the power of your cycle by living in sync with each phase!