What is Menopause
Most of us think we know what menopause is.
I thought I did.
For most of my life, I believed menopause was the years of changing hormones, irregular periods, hot flushes, poor sleep and mood swings. I wasn’t alone. We routinely use the word menopause to describe the entire hormonal transition of midlife.
Medically, however, menopause is something much more specific.
Menopause is not a phase that lasts for years. It is not a collection of symptoms, and it is not something you are continually “going through.” It is one point on the reproductive timeline: the final natural menstrual period, confirmed retrospectively after 12 consecutive months without another period, provided there is no other medical reason for menstruation to have stopped.
That means you cannot know on the day of your final period that it was your last. Only one year later can menopause be confirmed.
Nothing dramatic happens at that twelve-month point. Your ovaries do not suddenly switch off and your hormones do not disappear overnight. The date is a clinical marker used to establish that ovulation and menstruation have permanently ended.
The average age of natural menopause in the UK is 51, although reaching it between 45 and 55 is generally considered within the usual range. Menopause before 45 is described as early menopause. When ovarian function is lost before 40, it requires medical assessment and may be diagnosed as premature ovarian insufficiency.
So what are the years of changing periods and fluctuating symptoms?
They are mainly perimenopause—the transition leading towards menopause. The years after menopause are postmenopause. These are not simply three different names for the same experience. They describe biologically different stages.
How one word became three
For generations, menopause was used as an umbrella term for the whole midlife transition. Women were said to be “going through the menopause,” and the phrase became embedded in everyday language. It was not that women misunderstood their bodies; medicine had not yet developed a consistent way to describe what they were experiencing.
The term perimenopause was appearing in medical writing by the 1960s, but it remained largely within specialist circles. The years before the final menstrual period were still commonly treated as menopause approaching, rather than as a distinct stage with its own physiology.
During the 1980s, research into reproductive ageing expanded. Scientists began documenting that the lead-up to the final menstrual period was not simply a steady decline in oestrogen. Ovarian function became variable. Ovulation occurred less consistently, progesterone production changed and oestradiol could rise sharply as well as fall. The defining feature was fluctuation, not a smooth hormonal descent.
By the 1990s, researchers increasingly recognised the need for shared terminology. If one study used “menopause” to mean the final menstrual period while another used it to describe several symptomatic years, their findings could not be compared reliably.
In 2001, an international group of experts met at the Stages of Reproductive Aging Workshop and created the STRAW framework. It organised female reproductive ageing around changes in menstrual cycles and hormone patterns. The framework was updated at STRAW+10 in 2011 as the evidence improved. These criteria still underpin much of menopause research and clinical thinking today.
The biology behind the milestone
Menopause results from the natural ageing of the ovaries and the depletion of ovarian follicles—the structures that contain immature eggs and produce important reproductive hormones.
The ovaries do not work alone. They are part of the hypothalamic–pituitary–ovarian, or HPO, axis: a feedback system connecting the brain and ovaries. The hypothalamus releases gonadotrophin-releasing hormone, which signals the pituitary gland to produce follicle-stimulating hormone (FSH) and luteinising hormone (LH). These hormones prompt the ovaries to develop follicles, ovulate and produce oestradiol, progesterone and inhibin. Those ovarian hormones then feed information back to the brain and pituitary.
As the follicle supply diminishes, the ovaries become less able to respond consistently. The pituitary releases more FSH in an attempt to stimulate them. During perimenopause this feedback system can be highly variable, which is why a single hormone test often reveals little. After the final menstrual period, ovulation and progesterone production cease, oestradiol settles at a much lower level and FSH generally remains high.
Menopause is therefore a point in time, but the biology surrounding it is a continuing process.
Does HRT stop menopause?
No. Hormone replacement therapy cannot prevent menopause, delay ovarian ageing or preserve the remaining follicles.
What HRT can do is supply hormones that the ovaries are no longer producing consistently or in sufficient amounts. It can relieve symptoms including hot flushes, night sweats, disrupted sleep and vaginal dryness. For some women, it also has important benefits for bone health. The decision to use it should be based on individual symptoms, health history, preferences, benefits and risks.
Sequential combined HRT can produce a regular withdrawal bleed when the progestogen phase ends. This is caused by the medication; it is not evidence of ovulation or the return of a natural menstrual cycle. Consequently, starting HRT during perimenopause can make the precise date of the final natural period difficult to establish. HRT also does not provide contraception.
Why the distinction matters
Calling the whole experience menopause may seem harmless, but it conceals what is actually happening.
It is largely during perimenopause that hormones can swing unpredictably and symptoms may appear, disappear and return in a different form. Postmenopause brings a different hormonal environment: fluctuation reduces, but lower hormone levels may continue to affect the brain, bones, cardiovascular system and genitourinary tissues. Symptoms do not obey a calendar, and they do not necessarily end when menopause is confirmed.
Menopause itself is not the years of uncertainty. It is the marker that tells us one biological stage has ended and another has begun.
Knowledge does not alter that biology. But it replaces one vague, catch-all word with a clearer understanding of what the body is doing—and why.
Sometimes, understanding is the first step towards feeling more in control again.