What is actually happening during perimenopause?
The symptoms of perimenopause are usually blamed on hormones, but that doesn't tell us much about what's actually happening inside the body.
Perimenopause isn't simply a time when the body produces less oestrogen. It's a period of transition during which the communication between the brain and the ovaries becomes increasingly variable. As that communication changes, menstrual cycles become less predictable and a wide range of symptoms may develop. Understanding this process helps explain why the experience of perimenopause can be so different from one person to the next.
Perimenopause is part of reproductive ageing
Perimenopause is a normal stage of reproductive ageing. It marks the transition between the reproductive years and menopause, during which the ovaries gradually become less responsive and menstrual cycles begin to change.
We're born with our lifetime supply of ovarian follicles. Over time, both the number and quality of these follicles decline. As fewer follicles remain, the ovaries respond less consistently to the hormonal signals that regulate the menstrual cycle. Ovulation becomes less predictable, and hormone production begins to vary from one cycle to the next.
Perimenopause and menopause are often used interchangeably, but they describe different stages. Perimenopause is the transition leading up to menopause, which can last for 5-10 years (or longer in some cases). Menopause itself is reached once twelve consecutive months have passed without a menstrual period. From that point onwards, a person is considered postmenopausal.
Although this transition is a normal part of ageing, there is no single pattern that everyone follows. Some people notice only subtle changes over a number of years, while others experience symptoms that have a greater impact on daily life.
Hormone levels become less predictable
One of the biggest misconceptions about perimenopause is that it's simply a gradual decline in oestrogen.
During the reproductive years, hormone levels rise and fall in a predictable pattern across each menstrual cycle. This pattern is coordinated by hormonal signals travelling between the brain and the ovaries.
As the ovaries become less responsive with age, the brain increases its production of follicle stimulating hormone (FSH) in an attempt to encourage follicles to mature. Sometimes the ovaries respond as expected, while other times they respond less consistently. As a result, ovulation becomes less predictable, and some cycles occur without ovulation at all.
Because progesterone is produced after ovulation, cycles without ovulation are associated with lower progesterone levels. Oestrogen, however, doesn't simply decline. It may remain relatively unchanged, fluctuate more than it once did, or even rise to higher levels during some cycles.
Rather than a smooth downward trend, hormone production becomes increasingly variable. This changing pattern helps explain why symptoms can vary from one month to the next, and why the experience of perimenopause is different for everyone.
Oestrogen affects more than the reproductive system
When we think about oestrogen, it's easy to think of it as a reproductive hormone. But its effects extend well beyond the ovaries and menstrual cycle.
Cells throughout the body contain oestrogen receptors, including those in the brain, bones, muscles, skin, blood vessels, bladder, and vagina. Oestrogen helps regulate a wide range of normal physiological processes within these tissues. As hormone levels become more variable during perimenopause, it's not surprising that changes may be noticed in many different parts of the body.
This is one reason the experience of perimenopause can extend far beyond changes to the menstrual cycle. Changes in sleep, mood, body temperature, concentration, vaginal health, urinary symptoms, bone health, and joint comfort can all reflect the broader role that oestrogen plays throughout the body.
Not everyone experiences the same symptoms, and the severity of symptoms doesn't necessarily reflect where someone is in the transition. Some people notice only subtle changes, while others experience symptoms that have a greater impact on daily life.
Understanding the transition
Perimenopause is often thought of as a time when hormone levels simply decline. In reality, it's a period of transition in which hormone production becomes increasingly variable as the ovaries become less responsive and the hormonal signalling that regulates the menstrual cycle begins to change.
Because oestrogen has effects throughout the body, these hormonal changes can influence much more than the menstrual cycle alone. They help explain why the experience of perimenopause can look so different from one person to the next, and why symptoms may appear, disappear, or change over time.
Understanding what's happening inside the body doesn't change the experience of perimenopause, but it can make it easier to understand why these changes occur and provide a foundation for making informed decisions about care.
