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Hormonal Changes

There are two phases of changing hormones leading to menopause, and the first begins when periods are still coming monthly.

When do hormonal patterns start to change?

Only recently has research established that symptoms like hot flushes and depressed mood, can begin early in the menopause transition, well before menstrual irregularities occur, and can continue well beyond the final menstrual period.1

Our 2021 original WLB research also documented that many people still getting a monthly period experienced several symptoms often associated with perimenopause.

Founder and Director, Menopause Clinic, Atrius Health
Asst. Clinical Professor, Harvard Medical School

The two phases leading up to menopause: Regular and Irregular Cycles

The first phase of hormonal changes, when periods are still coming monthly — but with subtle changes to the length, days of flow, or amount of flow — is often misunderstood. This phase begins before periods are skipped and cycles are noticeably irregular. It’s called the Late Reproductive Stage (LRS). Following the LRS is the Menopausal Transition (MT) also referred to as perimenopause.

Regular Cycles (LRS)*

Hormonal changes
  • Estrogen levels are erratic with higher-than-normal, chaotic spikes throughout the cycle.2
  • Progesterone levels can be lower due to anovulatory cycles.2
  • The length of the cycle shortens by a day or two over many cycles and the days of flow may be fewer even though cycles are regular, coming every month.
Possible symptoms
*Periods are still coming monthly, but there are subtle changes to either cycle length (the number of days between periods), the amount of menstrual flow, or the number of days of flow.

Irregular Cycles (MT)

Hormonal changes
  • Estrogen levels begin to decline but may be erratic and high at times
  • Progesterone continues to decline due to more frequent anovulatory cycles
  • The onset of skipped periods
Additional symptoms
Note: The progression through these two phases is not necessarily linear as the timeline with the arrow might imply.
For example, some people will skip a period and then start getting regular periods again. Others will go several months without a period and then have periods restart. One ob-gyn we spoke to likens it to a Shakespearean death scene (you think the character is done, but they come back with a few more lines when you least expect it).

Each person’s experience is unique. Fluctuating hormones can lead to a wide variety of symptoms.

Common Symptoms

What’s happening with my hormones? A re-cap:

The first phase — when periods are regular — is not a time of declining estrogen. This phase is characterized by higher, spiking, and erratic estrogen levels2,3,4 — and it is not until later, as a woman is closer to menopause and experiencing skipped periods, that estrogen levels decline.

Progesterone levels decline in the years leading up to menopause as a result of less-robust, or lack of, ovulation.

We thought menopause was something that happened much later. We were in our early 40s and our periods were regular, so it didn’t cross our minds to attribute our disrupted sleep and new mood issues to hormonal changes.
WLB Founders, Nina and Jo

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“This is not me! When do I get my self back?”
Professor of Endocrinology and Metabolism, University of British Columbia
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How hormonal patterns change over time

A woman’s hormonal patterns across the lifespan can be thought of as three chapters.

And really there is a Chapter 0 that begins when a girl has had her first period (menses). It lasts until her hormonal patterns settle into a regular rhythm and her cycle becomes more predictable as in Chapter 1 (below). This phase is called puberty. The official name for the first period is menarche.

Chapter I:
Predictable Cyclicality

(aka the reproductive years)

Cycles stabilize a few years after the first period (menarche) and, in theory, hormones move in predictable patterns creating a typical menstrual cycle. Repeating that cycle over 6 months (180 days) would look something like this:

This phase is also sometimes called premenopause.

Chapter II:
Unpredictable Chaos

(aka the menopause transition)

Hormonal patterns begin to change in the late 30s/early 40s — due to the fluctuating, often higher than before estrogen, and occasionally lower progesterone. These fluctuations cause things look (and often feel) chaotic.

perimenopausal hormonal fluctuations

This phase is referred to as the menopause transition or perimenopause.

This is a visual depiction of data from a single woman as reported in Santoro N, Brown JR, Adel T, Skurnick JH. J Clin Endocrinol Metab. 1996 Apr; 81(4):1495-501. With permission from Nanette Santoro.

Chapter III:
Relative Stability

(aka menopause)

After menopause, the ovaries no longer produce follicles so the hormones that rose and fell to govern cycles stay at even levels. Low levels of estrogen continue to be produced by the adrenal glands and in fatty tissue.

A woman in this phase is said to be “in menopause” or post-menopausal.

Note: These are based on similar graphics from the September 1999 issue of Harvard Women’s Health Watch.

I am so in the throes of shifting hormones. Got my period on day 21 — a precipitous crash of hormones, cannot think straight. Amazing how not functional I am mentally. I know it will pass but am hiding out at home today. Knowing that this is “normal” is truly helping me cope.
WLB Community Member

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REFERENCES

1. Gracia CR, Freeman EW. Onset of the Menopause Transition: The Earliest Signs and Symptoms. Obstet Gynecol Clin North Am. 2018 Dec; 45(4):585-597. doi: 10.1016/j.ogc.2018.07.002. Epub 2018 Oct 25.

2. N. Santoro, J. R. Brown, T. Adel, and J. H. Skurnick, Characterization of reproductive hormonal dynamics in the perimenopause, Journal of Clinical Endocrinology & Metabolism, 1996, volume 81, issue 4, pages 1495–1501.

3. Jerilynn C. Prior, Perimenopause: The Complex Endocrinology of the Menopausal Transition, Endocrine Reviews, 1998, volume 19, issue 4, pages 397–428.

4. Georgina E. Hale, Xue Zhao, Claude L. Hughes, Henry G. Burger, David M. Robertson, and Ian S. Fraser, Endocrine features of menstrual cycles in middle and late reproductive age and the menopausal transition classified according to the Staging of Reproductive Aging Workshop (STRAW) staging system, Journal of Clinical Endocrinology and Metabolism, 2007, volume 92, issue 8, pages 3060–3067.

5. Karl R. Hansen, Nicholas S. Knowlton, Angela C. Thyer, Jay S. Charleston, Michael R. Soules, and Nancy A. Klein, A new model of reproductive aging: the decline in ovarian non-growing follicle number from birth to menopause, Human Reproduction, 2008, volume 23, issue 3, pages 699–708.

SOURCES

Estrogen’s Storm Season: Stories of Perimenopause, Dr. Jerilynn Prior, 2005
Our Bodies, Ourselves: Menopause, The Boston Women’s Health Collective, 2006
The Wisdom of Menopause, Christiane Northrup, MD, 2012
The Merck Manual: Menopause, consumer version, professional version