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What is perimenopause?
Understanding the transition, hormone fluctuations, and what to expect
Part 1 of 5: Perimenopause Awareness Month Series
Perimenopause is a transitional life stage—not a syndrome or a disease—that occurs as the ovaries approach menopause.*
It may begin earlier, last longer, and have more impact on people’s lives, bodies, and how they feel than many of us expect.
It follows the reproductive stage of life and officially ends when menopause is reached.
What is menopause?
Menopause is the point when someone has had their final menstrual period. It is confirmed retrospectively after 12 consecutive months without a period, provided there is no other reason for menstruation to have stopped.
Although “menopause” is sometimes used to describe the broader transition, each stage has distinct meanings. Perimenopause is the transition leading up to menopause, while postmenopause is the stage after the final menstrual period.
Perimenopause looks different for everyone
How people experience perimenopause varies just as much as how people experience menstruation, reproduction, sexuality, and other parts of life influenced by hormones, reproductive systems, brains, life histories and circumstances, and genetics.
The hormonal changes that happen during perimenopause can affect how someone feels physically and emotionally. A long history of marginalization and limited understanding of this life stage can also make it harder for people to recognize what is happening and get the support they need.
Because everyone’s experience is unique, and access to healthcare and education varies, there’s no single approach that will help everyone. What one person needs can be completely different from what someone else needs.
What helps one person with a symptom—for example, disrupted sleep—may not help another.
*Not everyone with ovaries experiences perimenopause in the same way. Removing both ovaries before natural menopause causes surgical menopause. Some medical treatments can also affect how the ovaries work, either temporarily or permanently. Removing the uterus but keeping the ovaries does not cause menopause right away. However, periods stop, which can make the transition harder to recognize. People with premature ovarian insufficiency (POI) may have menopause-related symptoms before age 40. However, POI is not the same as natural menopause because the ovaries may still work from time to time.
How do hormones change during perimenopause?
Your hormones don’t follow a straight line.
A lot of people think that the transition from perimenopause to menopause involves a steady, gradual decrease of estrogen until there’s none left.
But that’s not quite how it works.
Hormonal changes during perimenopause are more like a rollercoaster than a slide. For some, the roller coaster is short and gentle. For others, it’s more like one that takes you on a longer, more unsettling journey.
Most people experience something in between: parts of perimenopause that are relatively easy, and some parts that aren’t. Estrogen levels can rise and fall unpredictably, sometimes reaching higher levels than before. Ovulation becomes less consistent, so progesterone levels also vary and are often lower during cycles when ovulation does not happen.
Hormone levels usually become more consistently low after menopause, although the body continues to produce some estrogen and other sex hormones.
Why do hormones become so unpredictable during perimenopause?
People are born with a finite number of immature egg cells, stored in the follicles in the ovaries. The number of follicles declines throughout life, with most lost naturally through a process called atresia rather than through ovulation.
As the number of available follicles falls, the ovaries produce less inhibin B—a hormone involved in regulating follicle-stimulating hormone (FSH). In response, FSH levels generally rise, but they can vary a lot from one cycle to the next.
This makes the communication between the ovaries and the hypothalamus (a part of the brain that helps regulate the reproductive system) less predictable. Follicles start to develop less predictably, and ovulation may happen earlier, later, or not at all. This can cause estrogen and progesterone levels to fluctuate a lot. These changes together contribute to irregular menstrual cycles in perimenopause.
How can these hormonal changes affect the body?
Hormonal changes during perimenopause can affect many parts of the body.
These are the impacts or "symptoms" of perimenopause, like hot flashes and night sweats, body shape or size changes, constipation, fatigue, or mood swings. Some people experience few or even none of these impacts in early perimenopause.
The role of estrogen and progesterone
Most of us learn about estrogen and progesterone in the context of periods, puberty, and pregnancy. But these hormones have effects beyond the reproductive system. Receptors for them are found throughout the body, including in the brain, bones, heart, blood vessels, and gastrointestinal system.
Estrogen
Estrogen is the name for a group of hormones. Estradiol is the main form produced by the ovaries during the reproductive years.
Estrogen is involved in the development of sex characteristics, including the development of the uterus and breast or chest tissue. It also plays an important role in the menstrual cycle by helping the lining of the uterus grow in preparation for a possible pregnancy.
Estrogen has other effects throughout the body. It also helps:
Maintain the tissue of the vulva, vagina, and urinary tract and support vaginal lubrication
Support bone strength by helping to limit bone loss
Regulate body temperature through its effects in the brain
Influence brain systems involved in mood, memory, and sleep
Affect blood vessels, cholesterol, and how the body responds to insulin
Support the health of skin and connective tissue
Progesterone
Progesterone is produced mainly after ovulation. It helps prepare and maintain the lining of the uterus for a possible pregnancy. If pregnancy doesn’t happen, progesterone levels drop, helping trigger the start of menstruation. If pregnancy does happen, progesterone plays an essential role in supporting it.
Because ovulation becomes less predictable during perimenopause, progesterone production also becomes less consistent.
Progesterone also has other effects throughout the body. It can:
Affect smooth muscle in the uterus and gastrointestinal tract
Influence body temperature after ovulation
Interact with brain systems involved in sleep, mood, and anxiety
During perimenopause, levels of estrogen and progesterone can fluctuate considerably. Because these hormones affect so many parts of the body, those changes can contribute to symptoms and experiences that go beyond changes to your period.
Up next in the series → Part 2: Timelines, stages & spotting the first signs of perimenopause.
