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Your Menstrual Cycle

A refresher on your menstrual cycle is helpful in understanding how hormonal patterns change on the path to menopause. 

Understanding your menstrual cycle

Your menstrual cycle, specifically cycle length, can be a key indicator of the beginning of perimenopause.

Why cycle length matters: Subtle changes to cycle length, for most people a shortening of cycle lengths, is a sign that changes on the path to menopause have begun. Another way to think of this is that your periods are getting closer together.

Other “subtle” changes: Changes to menstrual flow are common as well. This can be a change in the number of days of bleeding — fewer or more.  Or you may notice a change in the amount of bleeding — more or less. And of course, you might notice a combination of these changes. You may start with a day of regular bleeding, then have a much heavier one, followed by two lighter-than-normal days.

Understanding your menstrual cycle may help you understand why you feel how you feel. See interpreting your menstrual cycle below.

DEFINING CYCLE LENGTH

Your cycle length is the number of days between your periods. It’s the number of  days between your first day of menstrual bleeding of one cycle and the first day of menstrual bleeding of the next one.

TRACKING YOUR CYCLE

How do you feel during the different parts of your cycle? If you are tracking your menstrual cycle this will be easier to figure out.

Tracking Your Cycle

A menstrual cycle hormone chart

There are three parts to a menstrual cycle:

Use your menstrual cycle to understanding perimenopause changes.
FOLLICULAR PHASE
  • Menstrual flow/bleeding (lasts from 1-7 days)
  • Low levels of estrogen and progesterone from the end of our last cycle cause follicle-stimulating hormone (FSH) to rise
  • FSH stimulates egg (follicle) development. A follicle is a cavity in the ovary containing a maturing ovum (egg) surrounded by its encasing cells. An average of 3-30 follicles mature per cycle
  • Developing eggs (follicles) produce estrogen, resulting in an estrogen surge
  • Estrogen causes growth of the endometrial lining
OVULATION
  • Estrogen surge causes luteinizing hormone (LH) to peak, which triggers ovulation
  • One “dominant” follicle (egg) bursts from the ovary
  • The remaining developed follicles die (called “atresia”)
  • The area on the ovary from which egg (follicle) appears is called the corpus luteum
  • Corpus luteum produces progesterone (and estrogen for the second half of a cycle)
LUTEAL PHASE
  • Progesterone enriches the endometrium to prepare for a fertilized egg
  • If no egg is fertilized, progesterone levels fall and endometrial lining is shed during flow
  • Next cycle begins
Note: In the chart above, we have put estrogen and progesterone on the same scale (y-axis) as most sources do. In reality, estrogen rises 220% above its day 1 level during a cycle, while progesterone rises 1,400%. This is not a typo! Estrogen levels are most often measured in picograms/milliliter, and progesterone in nanograms/milliliter (1 picogram = .001 nanograms).

Interpreting your menstrual cycle changes and symptoms

In premenopause:
  • Low hormone levels occur at the beginning and end of the menstrual cycle. How do you feel during those times?
  • Progesterone is only present in the second half of the cycle (luteal phase) when ovulation occurs. It usually peaks one week before bleeding occurs. For some, this is a time of low mood.
  • Estrogen peaks first right before ovulation (follicular phase) and then drops. It peaks a second time but usually less of a peak in the second half of the cycle (luteal phase).
  • Dropping estrogen effects. Many of us are sensitive to dropping estrogen. For example, menstrual migraines often occur right before the period when estrogen levels are dropping. Some people experience night sweats right before their period begins.
In perimenopause:
  • Shortening cycles can mean associated symptoms are happening more frequently.
  • Estrogen and progesterone work together so when the amount of each changes, new symptoms can arise.
  • Higher estrogen can lead to sore breasts and heavier menstrual flow.
  • Sharper drops from higher estrogen can mean more migraines.
  • Progesterone has different effects on different people. It can be calming for some and depressive in others so as it lessens mood symptoms can occur.

Learn more about menstrual cycle basics

From our founders:

WLB Founder’s Personal Story about Menstrual Cycle Changes

The “Learn More, Feel Better” series:
  1. Can You Picture Your Cycle? (i.e. how our menstrual cycles work)
  2. What Changes, When, and Why? (i.e. how our cycles change as we enter the many-year menopause transition)
  3. This Isn’t Me! (i.e. why some of us feel “so not like ourselves” )
Featured article:

Why We Don’t Expect Menopause-related Changes Before 45

RESOURCES

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