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The Menstrual Cycle


Women are cyclical. Unlike the hormones of males, the female hormones rise and fall throughout the month long process of menstruation (broken down into 4 phases), and these changes in hormones influence our brain, metabolism, immune system, gut health, and more.

The menstrual cycle is determined by the ovaries, progesterone (not estrogen) is the key hormone for period health, and it all starts with a follicle.

The entire process is a physical feat that requires adequate energy, minerals, and vitamins for a healthy cycle to occur and for conception and pregnancy to take place.

The timing of your cycle comes down to the sum of each phase’s length – typically between 21 and 35 days, with 28 days being the average length.

Each ovarian follicle contains one egg and takes 100 days to develop from dormancy to ovulation. This means that you can have period problems months after the follicle was affected (from any stressors) at any point during those 100 days of maturation.

For example, if you came down with an illness, you might notice changes in your cycle 2-3 months thereafter.

This is why your cycle can be a great tool when assessing your body’s ability to mitigate stressors and create and utilize energy.

Understanding how the menstrual cycle works, the changes the body undergoes, and how to best support this vital process is also important when it comes to how we choose to eat, move, and live.

This concept of synching your life to your cycle can have a huge impact in your ability to regulate your cycle by balancing hormones, as well as help you maintain a healthy weight, gain muscle, and improve mental and emotional wellbeing.

Two Halves

Lisa Hendrickson-Jack, a fertility awareness educator, calls the menstrual cycle “The Fifth Vital Sign.”

As women we can take a closer look at our menstrual cycle for insight into our health, specifically our progesterone and stress levels.

Before we dive into the specifics of each phase, let’s do a quick overview of the cycle into parts.

The first have of our cycle consists of the Follicular and Ovulatory phases.

During the first have of your cycle is a time of low hormones, until just before ovulation, when estrogen rises. This causes a slower metabolism and this slight decrease can be observed by your basal (resting) body temperature. It will typically be a little lower during the first half of your cycle, around 97.6 degrees.

The second half of your cycle is a your is a time of high estrogen and high progesterone synthesis, and consists of the Luteal and Menstrual phases.

During the second half of your cycle, the ovaries (via the corpus luteum) produce progesterone which boosts the metabolism. The increase in metabolism can come with an increased appetite – the energy required for the creation of the corpus luteum (as well as conception, if it has occurred) should be respected and honored. Ignoring the natural need for more nutrients during this phase (like trying to stick to some calorie count or diet) directly opposes the natural rhythm of your cycle.

Very long or short cycles (greater than 35 days and less than 21), PMS and painful periods, no ovulation, and bleeding midcycle can all signal an imbalance that needs to be addressed.

The best approach is to consider the “The ovarian-adrenal-thyroid (OAT) axis.”

These three hormone producing glands all work together, which is why when it comes to cycle health birth control cannot and will not fix these imbalances, but will only mask the issues at hand and contribute to more dysfunction.

Instead, a holistic view of the many systems involved in hormonal health is necessary to address the root cause.

Follicular Phase

It all starts with the follicle and takes 100 days to mature, during which our lifestyle impacts the health of our follicles. As Lara Briden explains, your period health is a long-term project. Just as everything we discuss when it comes to eating for cellular energy and health - it's a lifestyle to be maintained.

The follicular phase is a time of low hormone production, until the end of the phase, just before ovulation, when estrogen rises.

The first day of your follicular phase (following your period), the hypothalamus signals the pituitary gland to begin releasing FSH (follicle stimulating hormone) that does just as it says – stimulates the follicles to grow.

This triggers the release and rise of Estradiol, a type of estrogen made and released from the ovaries.


Boosts serotonin and dopamine

slows the metabolism

Enhances sensitivity to insulin

Stimulates the endometrium (uterine lining) to grow and thicken

Stimulates the discharge of fertile cervical mucous

The more estradiol you have, the thicker the endometrium, and the heavier your periods.

Fertile cervical fluid typically occurs prior to and during ovulation towards the end of the follicular phase to support the health of possible sperm.

However, it's important to know that fertile fluid can be observed anytime estrogen rises. If you have a longer follicular phase due to hormonal imbalances from stress, you may notice fertile mucous without ever ovulating because of the estrogen rising and falling.

This is also seen in postpartum and breastfeeding moms as you await the return of your cycle, and in perimenopausal women.

Understanding fertile fluid (and ovulation - which we will get to) is necessary when it comes to understanding your cycle and either avoiding or becoming pregnant. Contrary to popular belief, you cannot get pregnant every day of your cycle.

In order for conception to occur, you need an egg, sperm, AND fertile fluid. The fertile fluid is what keeps the sperm healthy and able to get to the egg.

Natural birth control methods using the tracking of cycle and fertile fluid are very effective in preventing pregnancy without the damaging repercussions of birth control.

Ovulatory Phase:

Moving into ovulation, estrogen is still rising, and this comes with an increase in LH (luteinizing hormone) which stimulates the release of the egg from one follicle (the other follicles are reabsorbed by the body), The egg will live for 24 hours only.

You may notice an increase in endurance and strength, and the ability to tolerate more intense workouts during this phase.

With estrogen at its peak point, you may also feel a higher libido and be more outgoing. The menstrual cycle is a conception driven process, so this makes sense because now that the egg is available, your body is ready to get to baby makin' (if that's your goal).

Ovulation is a big deal, because this is the main way we make progesterone – which is truly THE female hormone and the preferred hormone for health.

I talk a lot about decreasing excess estrogen, but we do want and need this hormone in the proper amounts, and progesterone via ovulation is an important component to this striking this balance.

When it comes to birth control, that intervention will permit a bleed, but stop ovulation which is a no go - because again, no ovulation = no progesterone. And the synthetic progestins within the birth control do not operate the same way the our hormones do.

Ovulation can be tracked using temperature, but you'll typically only know you ovulated after the fact, because there is a slight dip in temperature just prior to then rise 24 hours after the release of the egg. This is why also tracking fertile fluid is also important.

Luteal Phase:

“Under good conditions, the (premenstrual) luteal phase of the monthly cycle resembles pregnancy, as a period of progesterone dominance, in which the abundance of progesterone causes cells to decrease their estrogen content. The luteal phase is actually the first stage of pregnancy, and if there is implantation of an embryo all of the processes that begin at ovulation progress continuously until childbirth occurs.” Dr. Ray Peat

The last part of the follicle development is the formation of the corpus luteum – a temporary endocrine gland within the empty follicle that secretes progesterone – formed in less than a day.

Progesterone is released and begins to rise from the corpus luteum and signaling to the pituitary gland to stop secreting FSH and LH.

Progesterone is the main hormone for cycle health.