The Menstrual Cycle - Phases, Hormones and Their Functions

Learn everything you need to know about your menstrual cycle. Understanding it is essential as it impacts every aspect of your well-being.

illustration of the menstrual cycle hormones and functions during each age in a woman's life

In this post, we will cover everything you need to know about your menstrual cycle.

Last updated October 2023

Key points covered:

  • The menstrual cycle starts with the first day of the period and ends when the next period begins
  • The brain, ovaries, and uterus work together and communicate through hormones (chemical signals sent through the blood from one part of the body to another) to keep the cycle going.
  • The first part of the cycle (follicular phase) prepares an egg to be released from the ovary and builds the lining of the uterus
  • The second part of the cycle (luteal phase) prepares the uterus and body to either accept a fertilized egg or to start the next cycle if pregnancy doesn’t occur


  • The menstrual cycle is more than just the period. In fact, periods are just the first part of your cycle.
  • Understanding the menstrual cycle is important because it can impact the body from head to toe. You can see changes in your hair skin, bowel movements, mental health, physical strength, libido, and so on.
  • Hormonal methods of birth control prevent some or all of the steps in the cycle from happening.

Sections in the article:

What is the menstrual cycle?

By definition, the menstrual cycle begins with the first day of your period, which is counted as ‘Day 1’ and ends just before the next period (bleeding).

It’s the female body’s way of preparing for a possible pregnancy every month.

Understanding your cycle is very important as it impacts every aspect of female well-being, including hunger and sleep.

As the hormones in your cycle change throughout the month, your body and mind also go through a number of changes.

How long is the menstrual cycle?

Menstrual cycles normally range from about 25 to 36 days. However, it can also be longer or shorter, in which case it is considered as an ‘irregular cycle’.

How many women have irregular cycles?

Only 10 to 15% of women have cycles that are exactly 28 days, and in at least 14% to 25% of women, cycles are irregular. Having an irregular cycle means that a cycle is either longer or shorter than the normal range of between 25 to 36 days. Usually, cycles are the most irregular in the years immediately after a woman starts to menstruate and before menopause.

What are the menstrual cycle phases?

There are 4 main phases in your menstrual cycle:

menstrual cycle chart by Dr Natalie Brown

Follicular Phase

Phase 1: Early Follicular phase (aka menstruation)

  • When: The Early Follicular Phase starts on the first day of the period until Ovulation and generally lasts around 14 days
  • What happens: During the early follicular phase you shed your uterine lining (bleeding) and your estrogen and progesterone levels are at their lowest point.
  • Common symptoms:  Abdominal cramps, fatigue, and brain fog.
  • Early Follicular Phase tip: Good nutrition and exercise can help alleviate many of the symptoms you may experience during menstruation. Light exercises such as yoga, or even a walk, have been shown to reduce cramps and soreness. In our article "Best workouts to do on your period" you can find a few suggestions. However, listen to your body.
  • Elara Care team's experience: In my personal experience, movement of any kind has significantly reduced menstrual cramps. Taking ibuprofen once a day, 3 days prior to my period starting, has also proven to be very efficient.  
Best Workouts to Do on Your Period | Elara Care
Working out on your period can often feel uncomfortable but there are things you can do to relieve yourself from cramps and more.

Phase 2: Late Follicular Phase

  • When: After the period, the uterine lining builds back up again (aka the proliferative phase)
  • What happens: During this phase, estrogen rises as an egg prepares to be released. While the ovaries are working on developing the egg-containing follicles, the uterus is responding to the estrogen produced by the follicles, rebuilding the lining that was just shed during the last period. This phase can also be called the "proliferative phase because the endometrium (the lining of the uterus) becomes thicker.
ovulation procedure step by step illustration
  • Common symptoms: The change in hormones during this time will affect your energy levels, strength, and mental focus.
  • Late Follicular Phase tip: This is the perfect time to push a little harder at the gym, network, and meet new people. Just be mindful of everything you say yes to and make sure to make time for rest.
  • Elara Care Team's experience: I feel like I have a lot more energy during this time. It's great for working out and sticking to my nutrition plan. However, the excess energy can sometimes make my mind feel like it's going at a million miles an hour, making it hard to concentrate on one thing. I've found that time blocking my work (scheduling it in my work calendar) helps me get things done. Learning

Ovulation phase:

  • When: About halfway through the cycle, around day 13-15  (but this can change cycle-to-cycle and you might even have the occasional cycle where you don’t ovulate at all).
  • What happens: The release of the egg from the ovary, mid-cycle. Estrogen peaks just beforehand, and then drops shortly afterwards. The dominant follicle in the ovary produces more estrogen with its increase in size. It can usually reach up to about 2 cm but can also be up to 3 cm at its largest right before ovulation. When estrogen levels are high enough, they signal to the brain causing a dramatic increase in luteinizing hormone (LH) which in turn causes ovulation (release of the egg from the ovary) to occur.
  • Common symptoms: During this phase, we are at our brightest, energetic, and social. However, some women also report experiencing ovulation cramps and depression. It is also worth noting that during this phase, an extremely common condition known as an ovarian cyst can form.
  • Ovulation Phase tip: Continue taking advantage of the surge in energy. Meet up with friends and have those difficult conversations at work.
  • Elara Care Team's experience: I take advantage of this time to meet up with friends. If possible I also try and schedule important meetings around this time as I feel much more positive. Like I can take over the world.

Phase 3: Mid-Luteal phase:

  • When: The time after ovulation and before the start of menstruation. It normally lasts between 14 to 16 days.
  • What happens: The body prepares for a possible pregnancy. Once ovulation occurs, the follicle that contains the egg transforms into a corpus luteum and begins to produce progesterone as well as estrogen, with progesterone levels peaking about halfway through the luteal phase. If an egg is fertilized, progesterone supports the early pregnancy, alternatively, the uterine lining starts to break down resulting in menstruation.
  • Common symptoms: Some women report starting to feel PMS symptoms as early as the mid-luteal phase. Energy levels can start dropping and you may feel less social. Your body temperature increases slightly and you will start burning more calories
  • Mid-Luteal Phase tip: Be mindful of your energy levels and ensure you get enough sleep. Endurance and conditioning training are great a this time.
  • Elara Care Team's experience: I generally feel a lot warmer on the train, so wearing a few layers so that I can remove them, helps me stay comfortable. I also find that my brain slows down slightly, making it much easier to focus on tasks that require prolonged concentration.

For more detailed information on the Luteal Phase, check out our complete article: Luteal Phase - What It Is and How It Impacts You

menstrual cycle phases, hormones and uterine cycle

Phase 4: Late Luteal phase

  • When: The late luteal phase happens around 7 days before your next period starts, typically extending from day 24 to 28 of a standard menstrual cycle.
  • What happens: Estrogen and progesterone gradually decrease. This hormonal shift signals the body that no fertilization has occurred. The drop in progesterone causes the uterine lining to break down and lead to menstruation.
  • Common symptoms: 80% of women experience PMS symptoms during this time. These may include mood swings, irritability, fatigue, bloating, breast tenderness, and sleep disturbances.
  • Late Luteal Phase tip: Continue to workout and move your body, but be mindful of your energy levels and make time for resting and recharging. Use nutrition to support and mitigate your PMS symptoms; i.e. include complex carbohydrates like whole grains, legumes, fruits, and vegetables to help maintain blood sugar levels and provide a steady energy supply, reducing fatigue and mood swings. Check out our article on what to eat during the luteal phase.
  • Elara Care Team's experience: Maintaining a routine really helps me stay consistent with my workouts. I'll do my best to get into the gym, even if I end up using the session to mobilize and stretch. However, on days when I'm feeling really tired, I prioritize sleep. I also make sure to eat protein with every meal and keep dark chocolate in my fridge for when I want a "dessert".
How to increase energy levels during the Luteal phase
The luteal phase starts post-ovulation and ends when menstruation starts. This phase of the menstrual cycle is often characterized by several symptoms, such as mood fluctuations, cravings, higher basal body temperature, and a dip in energy levels, to name a few. However, there are strategies you can…

What hormones are involved in the menstrual cycle?

The menstrual cycle is regulated by several different hormones. But the main ones are:

  • Follicle-stimulating hormone (FSH): Stimulates egg development and the release of estrogen.
  • Luteinizing hormone (LH): Stimulates the release of the egg (called ovulation). Stimulates estrogen and progesterone production.
  • Estrogen: causes growth of the uterine lining. Inhibits FSH. Stimulates the release of LH and hence the release of the egg. Inhibits LH after ovulation.
  • Progesterone: maintains the uterine lining. Inhibits LH after ovulation.
video gif of the menstrual cycle working

Breakdown of hormones and their functions in the menstrual cycle

Follicle stimulating hormone

Follicle-stimulating hormone is produced by the pituitary gland. It regulates the functions of both the ovaries and the testes. Lack or insufficiency of it can cause infertility in both men and women.

What is a follicle-stimulating hormone?

Follicle-stimulating hormone is one of the gonadotropic hormones, the other being the luteinizing hormone, and both are released by the pituitary gland into the bloodstream.

Follicle-stimulating hormone is essential to pubertal development. In women, this hormone stimulates the growth of ovarian follicles in the ovary before the release of an egg and it also increases a type of estrogen.


What is estrogen?

Oestrogen is one of the main female sex hormones. While both women and men produce estrogen, it plays a bigger role in women’s bodies.

It has many roles in the body, from controlling puberty to strengthening bones. Having too much or too little estrogen can cause a range of different medical conditions.

There are three estrogens – oestrone, oestradiol, and oestriol – the most potent of which is oestradiol.

  • Oestradiol is produced in women of childbearing age, mostly by the ovaries.
  • Oestriol is the main estrogen produced during pregnancy, mostly in the placenta.
  • Oestrone, produced by the adrenal glands and fatty tissue, is the only type of estrogen produced after menopause.


What is oestradiol?

Oestradiol is a steroid hormone made from cholesterol and is the strongest of the three naturally produced estrogens. It is the main estrogen found in women and has many functions, although it mainly acts to mature and maintain the female reproductive system. A natural increase in blood oestradiol concentrations during the menstrual cycle causes an egg to mature and be released.

Another important role of oestradiol is to thicken the lining of the uterus so that the egg can implant if it becomes fertilized. Oestradiol also promotes the development of breast tissue and increases both bone and cartilage density.

In premenopausal women, oestradiol is mostly made by the ovaries. Oestradiol levels vary throughout the monthly menstrual cycle, being highest at ovulation and lowest at menstruation. Oestradiol levels in women reduce slowly with age, with a large decrease occurring at menopause when the ovaries ‘switch off’. In pregnant women, the placenta also produces a lot of oestradiol, especially toward the end of the pregnancy.

Men also produce oestradiol; however, the amounts produced are much lower than in women. Within the testes, some testosterone is changed into oestradiol and this oestradiol is essential for the production of sperm. In both sexes, oestradiol is also made in much smaller amounts by fat tissue, the brain, and the walls of blood vessels.

Luteinizing hormone

What is the luteinizing hormone?

Luteinizing hormone, like a follicle-stimulating hormone, is a gonadotrophic hormone produced and released by cells in the anterior pituitary gland.

It is crucial in regulating the function of the testes in men and ovaries in women.

In women, the luteinizing hormone carries out different roles in the two halves of the menstrual cycle. In weeks one to two of the cycle, luteinizing hormone is required to stimulate the ovarian follicles in the ovary to produce the female sex hormone, oestradiol.

Around day 14 of the cycle, a surge in luteinizing hormone levels causes the ovarian follicle to tear and release a mature oocyte (egg) from the ovary, a process called ovulation.

For the remainder of the cycle (weeks three to four), the remnants of the ovarian follicle form a corpus luteum.

The luteinizing hormone stimulates the corpus luteum to produce progesterone, which is required to support the early stages of pregnancy if fertilization occurs.


What is progesterone?

Progesterone belongs to a group of steroid hormones called progestogens. It is mainly secreted by the corpus luteum in the ovary during the second half of the menstrual cycle.

It plays an important role in the menstrual cycle and in maintaining the early stages of pregnancy.

During the menstrual cycle, when an egg is released from the ovary at ovulation (approximately day 14), the remnants of the ovarian follicle that enclosed the developing egg form a structure called the corpus luteum. This releases progesterone and, to a lesser extent, oestradiol.

Progesterone prepares the body for pregnancy in the event that the released egg is fertilized.

If the egg is not fertilized, the corpus luteum breaks down, the production of progesterone falls and a new menstrual cycle begins.

If the egg is fertilized, progesterone stimulates the growth of blood vessels that supply the lining of the womb (endometrium) and stimulates glands in the endometrium to secrete nutrients that nourish the early embryo.

Progesterone then prepares the tissue lining of the uterus to allow the fertilized egg to implant and helps to maintain the endometrium throughout pregnancy.

During the early stages of pregnancy, progesterone is still produced by the corpus luteum and is essential for supporting the pregnancy and establishing the placenta. Once the placenta is established, it then takes over progesterone production at around weeks 8-12 of pregnancy.

During pregnancy, progesterone plays an important role in the development of the fetus; it stimulates the growth of maternal breast tissue; prevents lactation; and strengthens the pelvic wall muscles in preparation for labor.

The level of progesterone in the body steadily rises throughout pregnancy until labor occurs and the baby is born.

Although the corpus luteum in the ovaries is the major site of progesterone production in humans, progesterone is also produced in smaller quantities by the ovaries themselves, the adrenal glands, and, during pregnancy, the placenta.


Your menstrual cycle is your personal algorithm of life. Take time to learn about how changing hormones impact you throughout the cycle (we call this menstrual cycle literacy) to understand how you can take advantage of your hormones instead of suffering through them.

You might also be interested in the following article:


  1. Fraser IS, Critchley HO, Broder M, Munro MG. The FIGO recommendations on terminologies and definitions for normal and abnormal uterine bleeding. Semin Reprod Med. 2011;29(5):383-90.
  2. Munster K, Schmidt L, Helm P. Length and variation in the menstrual cycle-a cross-sectional study from a Danish county. BJOG. 1992;99(5): 422–9.
  3. Treloar AE, Boynton RE, Behn BG, Brown BW. Variation of the human menstrual cycle through reproductive life. Int J Fertil. 1967;12(1 Pt 2):77-126.
  4. Fehring RJ, Schneider M, Raviele K. Variability in the phases of the menstrual cycle. JOGNN. 2006;35: 376-384.