Understanding Your Menstrual Cycle in Perimenopause

menstrual cycle in perimenopause

The aim of this blog is to help you to understand what’s different about your menstrual cycle in your 40s.

Your reproductive (menstrual cycling) years start from your first ever period as a teen right up to menopause but your cycle starts to change from age 35, and by your late 30s or early 40s, symptoms and changes are staring to manifest.

The menstrual cycle, from teens to menopause (when your periods stop for good), is dictated by the communication between your brain and your ovaries. All month long, your brain talks to your ovaries to conduct the production of oestrogen and progesterone, at the right times, to stimulate ovulation and prepare the uterine lining to hold a pregnancy.

However, fertility aside, this hormonal dance is essential to female health and we want it to occur month after month (halting when pregnant) until menopause. 

Simply put, making oestrogen and progesterone at the right times throughout the month safeguards many aspects of health including metabolic, cardiovascular, bone, immune and cognitive.

Phases of womanhood

Table showing the 5 phases of womanhood related to the menstrual cycle.

What you can see in this table is that regular reproductive years start from the first ever period as a teen, all the way up to perimenopause, which starts from around age 35 up to menopause (average age 51). Menopause itself lasts for one day, then you are in the post-menopause phase from there on in.

Throughout perimenopause, you continue to have cycles (have periods), which are still regular (at least at first) and you are still fertile – albeit not as fertile as in your 20s and 30s.

What’s different in perimenopause is the communication between your brain and ovaries. From age 35 it’s starting to change or somewhat break down, causing changes to your menstrual cycles and periods for example, making your cycles irregular, longer or shorter and making your periods heavier and or painful or longer or shorter.

You may also notice new or worse PMS such as breast pain or tenderness, mood swings and even rage, low energy and sleep issues. Sounding familiar?

Growth of fibroids and cysts can also be common here.

Your menstrual cycle before and during perimenopause

The menstrual cycle in your 20s and 30s

Your 20s and first half of your 30s sees a more gentle ebb and flow of oestrogen, as per the diagram below.

The menstrual cycling during regular cycling years

In this diagram, we see that oestrogen dominates in the first half (follicular phase), ramping up just before ovulation to stimulate the release of an egg and then progesterone dominates in the second half (luteal phase). Progesterone is ONLY made after ovulation, which in a normal cycle, should occur about half way through (approx day 12 or 13). A few days before your next period is due, both hormones fall to their lowest levels in the cycle until your period starts (marking day 1 of a new cycle) and oestrogen starts to climb gradually again. 

During the first 14 days (from day 1 of your period), the follicular phase, follicle stimulating hormone (FSH) stimulates your follicles to produce oestrogen. During this phase, oestrogen is building up the tissue in the wall of your uterus, almost like building the bricks for a healthy, fluffy endometrium in preparation for implantation and housing of a fertilised egg. Oestrogen surges just before ovulation (in order to assist ovulation to occur).

Then, in the last two weeks of the cycle (the luteal phase), progesterone comes along to make sure oestrogen doesn’t pile up too many bricks and, like mortar, progesterone stabilises the wall (uterine lining).

The release of progesterone shuts down oestrogen production and ensures the next menstrual period doesn’t start too early or that any irregular/early spotting occurs.

Progesterone protects your uterus from developing too much of an inner lining from the exposure to oestrogen. It does this by making sure the cells of the uterine lining shift from “grow, grow, grow” to “mature and prepare for the next stage”, which is either menses or Pregnancy.

Without progesterone (due to no ovulation occurring in that cycle) to prevent too much thickening of the inner lining, a heavy period with clotting is likely the result.

How you make progesterone and why it’s about SO MUCH more fertility

After ovulation, a mature ovarian follicle ruptures. This ruptured follicle transforms into a temporary endocrine gland known as the corpus luteum. Ovulation is essential to the production of this gland, and this gland is essential for progesterone production.

The role of progesterone is to support pregnancy should your egg become fertilised. BUT! Fertility aside, we WANT to make progesterone every single month because it also balances oestrogen, preventing oestrogen dominance in the second half of the cycle, which causes things like mood swings, breast pain, horrible periods, headaches and sleep issues.

Additionally, progesterone is important for your overall sense of equilibrium and well-being, it provides contentment, supports sleep, boosts metabolism and thyroid function, prevents fluid retention and supports cognition. It increases the calming, anti-anxiety brain chemical GABA, which calms the nervous system and promotes good sleep.

Your cycles can still appear normal even though you haven’t ovulated, these are called non- or an-ovulatory cycles. One way to see if you have ovulated in any given month is to track your basal (first thing upon waking) body temperature. When progesterone is made (after ovulation) your body temperature rises slightly and so seeing a slight increase in temperature around ovulation time and for the rest of that cycle is a good indicator of having ovulated (and therefore having made progesterone).

A big indicator of having NOT ovulated is new or worse PMS followed by a heavier and or painful period – which would have been caused by oestrogen being left alone to dominate the second half of your cycle instead of being balanced out with progesterone as it should be.

The menstrual cycle in perimenopause

Perimenopause is much rockier and more difficult than menopause, because hormones fluctuate, month-to-month, sometimes mildly and sometimes wildly.

The menstrual cycle through the lifespan (including perimenopause)

In this diagram, you can see the gentle ebbing and flowing of oestrogen in the reproductive years (the red dotted line) compared to an erratic roller coaster in perimenopause. What you can also see is healthy, consistent progesterone (blue line) in your 20s and 30s compared to a decline of this wonderful hormone in perimenopause.

The change in brain to ovary communication in perimenopause creates three main issues with oestrogen that cause many of the symptoms and changes experienced here, they are;

  1. Erratic fluctuations (the oestrogen roller coaster)
  2. Oestrogen dominance in the second half of the cycle
  3. Oestrogen excess

As part of the roller coaster, the highs can see oestrogen levels 3 times higher than ever before (as shown in the above diagram) followed by it crashing down to almost nothing.

These erratic highs and lows bring changes to your cycles and periods, such as;

  • New or worse PMS including mood swings (including rage!)
  • Breast pain
  • Heavy and or painful periods
  • Clotting, cysts
  • Headaches or migraines
  • Sleep issues
  • Anxiety
  • Brain fog
  • Low energy and fatigue
  • Hot flushes and night sweats
  • Histamine or mast cell reactions

Add to this, symptoms of having not made progesterone, some or many months, such as:

  • Insomnia
  • Anxiety
  • Irritability
  • Migraines
  • Water retention / puffiness
  • Irregular periods, shorter cycles and spotting between periods

It’s a rocky road to menopause

During your regular reproductive years (approx 18-35), progesterone calmed the nerve cells in your brain and nervous system and stimulated a molecule called BDNF, which is important for cognition, e.g., clarity, memory and learning.

Oestrogen supported the energy system of the brain by allowing glucose to efficiently get into your brain cells for energy, it stimulated the mitochondria in your brain cells (tiny energy powerhouses), reduced inflammation, regulated your circadian rhythm (for good sleep) and boosted the happy chemical serotonin.

Research suggests that the brain undergoes a massive rewiring process during perimenopause and the first few years of menopause, which causes many of the symptoms and makes them more pronounced during the recalibration phase.

So, early menopause can be thought of as a temporary ‘energy crisis’ while the brain adjusts and recalibrates and once readjusted, there should be no more symptoms (for most)!

It’s like second puberty!

For the first couple of years or so as a teen, your brain to ovary communication was adjusting to moving into the reproductive years – oestrogen was fluctuating erratically and progesterone wasn’t always made. Remember the irregular cycles, heavy, painful periods, clotting, breast tenderness, PMS through the roof with headaches and mood swings as a teen?

Well, from age 35, brain and ovary communication starts breaking down in a similar way to what was happening at puberty, causing many of the same symptoms all over again and this is how we can liken perimenopause to ‘second puberty’ or ‘puberty in reverse’!

What can you do?

Whilst perimenopause IS a natural transitional phase, it’s also phase of biological rough waters. BUT…it CAN be navigated optimally with a smart captain at the helm of the ship (You!)

Symptoms are temporary (thank goodness!) and respond to simple diet and lifestyle habit interventions that can support the 3 main issues with oestrogen and the production of progesterone (ovulation) as many months as possible.

It is up to you to decide whether or not you want to take action and make the changes necessary for a MUCH smoother and enjoyable ride in your 40s AND transition into menopause and post-menopause when the time comes.

In perimenopause, you want to leverage diet and lifestyle habits that can help to:

  • prevent the oestrogen rollercoaster from spiking too high and too low, which will keep symptoms of high and low oestrogen in much better check
  • Prevent oestrogen dominance by helping your body to make progesterone as many months as possible (by supporting ovulation)
  • Support ovulation so that you make progesterone for its wonderful symptom-reducing and health-protective benefits
  • Prevent or reverse (manage) insulin resistance, which makes all symptoms worse, puts your current and future health at risk and results in excess belly fat

Read my previous blog called ‘How to Get Rid of Perimenopausal Symptoms’ here for tips on what you can do!

Hi, I'm Francesca

I’m a Registered Nutritional Therapist who helps womens in their 40s find vibrant health and vitality, and thrive through perimenopause and beyond.

With nearly 10 years of experience working with hundreds of people, I empower and support women to support their bodies and hormones for a smooth and happy ride in their 4os.

Through our work together, clients have improved their energy, their periods and cycles, their mood, sleep, brain fog and digestion, and learned how to better manage their weight.

I am here to help you get back to YOU so you can have a fantastic time in your 40s.

My signature nutrition and lifestyle coaching approach to supporting women with their health and wellbeing is refreshing, down-to-earth and realistic.

Download the Free Guide

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Learn more about my signature course – Thrive Through Perimenopause – to start taking care of your hormone health once and for all, for a MUCH smoother ride in your 40s and beyond!

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