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What is Perimenopause? Understanding the First Phase of Menopause

Updated: Apr 25

Discover what perimenopause is and how it can affect many aspects of your life. Discover how HRT and lifestyle habits for life and reduce your symptoms, improve quality of life and reduce long-term disease risks.

What Is Perimenopause?

Perimenopause is the transitional time period leading up to menopause. It typically starts in a woman's late 30s to late 40s. During this time, hormone levels fluctuate and decline, causing physical and emotional changes. Perimenopause is an ill-defined time period. It is estimated to last between 5 and 10 years. The medical definition of perimenopause begins with the first onset of menstrual irregularity and ends after 1 year of no periods.

Perimenopause can begin before this time if a woman is heading into premature ovarian insufficiency (when the periods stop before age 40) or early menopause (when the periods stop before age 45) due to reduced ovarian hormone production.

Hormonal perimenopause can continue into the late 50s. This is the phase when ovarian production of hormones winds down to a low level similar to pre-puberty.

Perimenopause Is A Neuro-Endocrine Transition

Perimenopause is a transition phase like other neuro-endocrine phases such as adolescence (the transition from childhood to adulthood) and matrescence (the transition to motherhood).

Each of these transitions encompass multiple domains of a woman’s life including:

  1. Biology: hormones, metabolism & physical symptoms

  2. Psychology: how she thinks and feels about herself, her self-identity and the world

  3. Social/Community: her important connections to others in her community, changes with relationships and roles at home and work

  4. Political: a woman’s place and value in her society as she moves from reproductive capacity to a non-reproductive phase and how she feels about this.

  5. Spiritual: her ongoing creativity, discovery and connection to purpose and meaning in life

  6. Sexual: changes in reproductive anatomy and function, sexual desire, pleasure & intimacy.

As we approach menopause there are changes that can be predicted and expected; we know our bodies will go through physically change. But less commonly acknowledged are the intense changes to our biology, identity, beliefs, values, independence, purpose and often relationships as women traverse perimenopause.

For some women it is a period of loss and grief for a part of their body and life that will never be the same. Other women experience it as a liberating experience. Experiences vary greatly as women find meaning in their journey through these changes.

It is important is to be open, generous and kind to yourself as you transition through perimenopause.

Perimenopause is a Critical Window of Health

Just as adolescence and pregnancy are seen as critical windows of health, perimenopause is a critical window of health that impacts the re-organization of 2 key neuroendocrine systems. (hypothalamic-pituitary-gonadal-HPG axis and hypothalamic-pituitary-adrenal-HPA axis) (Till Hoyt, 2015).

Many women are at increased risk of developing long term health conditions such as mood disorders, metabolism, cardiovascular health, bone health, autoimmune disease and cancer during perimenopause (Till Hoyt 2015).

Comprehensive and holistic perimenopausal treatment should consider each of these interconnected areas of a woman’s life to support women to thrive as they transition to the next exciting phase of their lives

perimenopausal woman snuggled on a sofa smiling

Stages of perimenopause (from a reproductive biological perspective!)

The reproductive biological phases of perimenopause are outlined below. Bear in mind that the ongoing psycho-social-politico-spiritual-sexual developmental changes, although initiated through hormonal change can be much more expansive in duration and may last much longer.

The exact length of such perimenopausal changes are individual to each woman and may arguably spur continued growth and development into the post-menopausal stage for her remaining lifetime!

Diagram of STRAW criteria for reproductive phases of women

Stages of normal reproductive ageing in women (Nelson 2008).

Early Perimenopause (can last 2-5 years+)

In early perimenopause, a woman’s ovaries initially will start to produce higher levels of estrogen. Very early perimenopause usually begins while women continue to have regular periods. Estrogen levels rise as more eggs are recruited and stimulated each cycle.

Although periods are regular women can still experience symptoms typically associated with higher estrogen/lower relative progesterone – 3 or more symptoms indicates perimenopause:

  1. New onset heavy and/or longer flow or pre-menstrual spotting

  2. Shorter menstrual cycles (25 days)

  3. New sore, swollen or lumpy breasts

  4. New mid-sleep wakening

  5. Increased cramps

  6. Onset of night sweats, in particular premenstrually

  7. New or markedly increased migraine headaches

  8. New/increased premenstrual mood swings/PMS – including menstrual headaches/migraines

  9. Weight gain without changes in exercise or eating.

Howevere there are a wide-range of symptoms of perimenopause that are common and that women can experience.

Early Perimenopause Phase

This stage occurs approximately 3-10 years prior to final period. It is a transition from regular to irregular periods.

Late Perimenopause Phase

This stage begins when the first cycle lengthens to 60 days or more.


The cessation of periods. It can only be know to have occurred retrospectively after the women’s periods have stopped for 12 months.


The phase of life after the 12 months after the final period.

Medical Menopause or Surgical Menopause

Some women experience menopause due to surgery such as ovary removal or medical treatment such as radiation therapy to the ovaries or taking an anti-estrogenic medication. This can be a dramatic hormonal drop and typically is usually supported with hormone replacement therapy.

Read about Menopause HRT funding in New Zealand.

Additionally for women who have a hysterectomy, there can be up to a 70% decrease in blood supply to the ovaries resulting in decline in ovarian function for 4-5 years after surgery. These women experience perimenopausal symptoms without periods.

Premature Menopause or Primary Ovarian Insufficiency

When the ovaries stop producing estrogen at a significantly earlier age than is typical, women experience either:

  1. Premature menopause or premature ovarian insufficiency = periods stop prior to age 40.

  2. Early menopause = periods stop between 40 and 45 (Rees 2022).

What Happens To The Sex Hormones In Perimenopause

Inhibin B is produced by undeveloped egg cells in the ovaries. With age-related decline in egg cells, inhibin B hormone production declines. This leads the pituitary gland to increase FSH production. Recognizing lower egg numbers it produces a higher kick of FSH to stimulate the ovaries to ripen eggs each month. This leads to relatively higher estrogen than progesterone and relative ‘estrogen dominant’ symptoms occur while the body is initially able to maintain ovulation (Burger, 2008).

At some point ovulation does not happen with every cycle. A cycle without ovulation is called an anovulatory cycle. With anovulatory cycles or with short ovulatory cycles progesterone is low and can cause heavy bleeding, prolonged bleeding, and can encourage the growth of the endometrial lining causing thickening and uterine polyps.

Anovulatory cycles showed markedly increased FSH with declining estrogen levels and inhibin B. There become more frequent through late transition and are typically the last cycles women have are all anovulatory.

Additionally due to higher and prolonged FSH stimulation during the early part of the cycle, many women have “luteal out of phase” (LOOP) cycles. This means they have erratic estrogen peaks – typically a second, higher estradiol peak after the normal midcycle estradiol peak during the luteal phase.

This creates relatively higher estrogen and lower luteal phase progesterone and can create exaggerated premenstrual symptoms and longer periods with heavier bleeding. These cycles occur in approximately 1/3 of cycles during early and late menopause transition (Prior 2011).

Symptoms of perimenopause

Perimenopause symptoms are common, often multiple and vary in severity and type between women and include (Makara-Studzińśka 2014):

  1. Hot flashes

  2. Night sweats

  3. Irregular periods, heavy periods, longer periods

  4. Vaginal dryness – this can lead to other symptoms such as urinary tract infections

  5. Mood swings and depression or anxiety,

  6. Weight gain

  7. Fatigue

  8. Sexual function disturbance

  9. Sleep disturbance

  10. Joint aches and pains

  11. Androgen symptoms – acne, mild facial hair growth, mild hair loss on head

  12. Dry skin, mouth and eyes

  13. Menstrual migraine/headache

  14. More exaggerated pre-menstrual symptoms (PMS).

Perimenopause and Mood Swing and Brain Health

Perimenopause is a critical neuro-endocrine window for long-term brain health. This means optimizing brain health during the 40s and 50s lays the foundation for brain health for the rest of a woman’s life (Brinton 2015). "Estrogen is the ‘master regulator’ of the female brain,” according to Lisa Mosconi, director of the Women’s Brain Initiative and associate director of the Alzheimer’s Prevention Clinic at Weill Cornell Medical College/New York-Presbyterian Hospital.

Estrogen pushes neurons to burn glucose to make energy and plays important roles in the plasticity of the brain and in immunity, keeping a woman’s brain younger and healthier.

As estrogen declines through perimenopause neurons start slowing down and age faster. This causes not only cognitive changes such as depression, anxiety and trouble concentrating, but other menopause-related symptoms.

The lack of estrogen in the hypothalamus impairs body temperature regulation, leading to hot flashes. The reduced estrogen in the brain stem contributes to insomnia. Reduced estrogen in the amygdala, the emotion-memory center of the brain, we can feel depressed, anxious, forgetful or what is described as brain fog.

Additionally the lack of progesterone plays a role in poor sleep, low mood and anxiety. One of the roles of progesterone is that it is metabolized in the liver to allopregnanolone. Allopregnanolone acts in the brain as a calming neurosteroid. Allopregnanolone reduces symptoms of anxiety, improves mood and improves sleep (Schüle 2014).

The decline in estrogen hormone levels is also associated with a slight increase in insulin resistance – discussed below, which has implications for increased risk of Alzheimer’s disease and is why this disease is sometimes called ‘type 3 diabetes’ (Duarte 2018).

Key approaches to improving brain and mental health as well as reducing risk of Alzheimer’s disease during perimenopause include:

  1. body-identical hormone therapy - estrogen, progesterone and possibly testosterone (more research is needed)

  2. exercise

  3. wholefood diets such as the Mediterranean diet

  4. strategies for stress management

  5. reducing alcohol and cigarette consumption

  6. maintaining normal blood pressure.

Perimenopause, Weight Gain And Metabolism

Women experience changes in body composition and metabolism as well as slower bone metabolism during perimenopause and after menopause.

Metabolic syndrome consists of:

  1. insulin resistance (the body needing to produce more insulin to control blood sugar levels),

  2. abdominal obesity,

  3. high cholesterol

  4. high blood pressure.

These conditions are proinflammatory and contribute to increased risks of clotting conditions (heart attack, stroke), diabetes and cancers (Salpeter 2005).

Metabolic syndrome is also known as insulin resistance syndrome. Metabolic syndrome can be improved or reverse with lifestyle changes.

The decline in estrogen through the perimenopause causes a number of changes to women’s metabolism and body composition including:

  1. decreased bone density

  2. decreased muscle mass and strength

  3. increased abdominal fat (visceral fat)

  4. lower insulin sensitivity

  5. relatively higher androgen (testosterone) (due to lower estrogen levels).

To improve insulin sensitivity and maintain muscle mass and strength during perimenopause and after menopause it is essential for women to participate in some form of resistance training 2-3 times that continues to strengthen muscle. This type of exercise also reduces frailty in old age.

Resistance training increases muscle strength by making your muscles work against a weight or force. This can be free weights, resistance bands, your own body weight or weight machines.

Simple resistance training without weights involves push-ups, squats chin-ups and burpees. Making use of a personal trainer is a great way to assess your strength and develop a resistance training plan for perimenopause.

Bone health

On average women lose 10 percent of bone density during the first 5 years after menopause. To maintain bone density (and improve insulin resistance) it is important to do weight-bearing exercise such as:

  1. jogging or running

  2. team and racket sports

  3. skipping, jumping

  4. dancing,

  5. mini-trampolining.

Swimming and cycling are not weigh-bearing exercises so although good for heart health, they do not improve bone health.

Additionally, meta-analysis of menopause hormone therapy (MHT) during perimenopause demonstrates that it improves all metabolic parameters including (Salpeter 2005):

  1. increased lean body mass (muscle mass)

  2. reduced waist circumference

  3. reduced abdominal fat

  4. reduced insulin resistance and blood sugars and fasting insulin in women without and with diabetes

  5. 30% reduction in the risk of developing diabetes.

  6. reduced LDL

  7. increased HDL

  8. Increased bone mass.

Of note oral menopause hormone treatment (MHT) increased CRP, a marker of inflammation but transdermal agents did not. Additionally estrogen alone increased CRP but combined treatment with estrogen and progesterone did not. MHT also reduces clotting factors such as fibrinogen and PAI-1.

Fertility and Pregnancy During Perimenopause

Female fertility and egg quality begins to decline from age 30. As women enter perimenopause there can be additional challenges with fertility due to shorter cycles with insufficient luteal phase and progesterone production to maintain a pregnancy. This can be supported with oral micronized progesterone or progesterone vaginal cream during the second half of the cycle and continued until 12 weeks of pregnancy.

Also women experience reduced fertility due to increasing anovulatory cycles where ovulation does not occur with every cycle.

Despite a decline in fertility, women can and do conceive during perimenopause, especially during earlier phases. Contraception is important during this time if you are sexually active in a heterosexual relationship and not wanting to be pregnant. To maintain ovulatory cycles as long as possible use of the IUD contraceptive such as the copper, Mirena or Jaydess for effective long-lasting contraception.

Reliable contraception is advised until menopause is confirmed either by a lack of periods for 2 years before age 50, or for 1 year after age 50 (Baldwin 2013).

After the age of 35 years, there is a higher risks during pregnancy of:

  1. pregnancy loss

  2. complications during childbirth and the need for a caesarean delivery

  3. preeclampsia

  4. having a child with a congenital/chromosome abnormality

  5. maternal health problems such as gestational diabetes or high blood pressure during pregnancy.  

Despite this many women do maintain fertility in early perimenopause and women do conceive and have healthy pregnancies. Read An integrative approach to conception for more information.

Hormone Replacement Therapy and Perimenopause

Many women use hormone replacement therapy (HRT) to support their quality of life, improve their sleep, support their mood and reduce hot flashes during perimenopause. It is an effective treatment and safe for most women.

There is a lot to get your head around when it comes to HRT, but here basics of HRT are covered. Talk to your health provider who can counsel you in depth about your individual health situation.

Lifestyle Hacks for Perimenopause

Perimenopause is a great time to take stock of your health and wellbeing and looking forward to establising great health habits for the rest of your life.

Read more about lifestyle habits for perimenopause including nutrition, exercise, stress management and more.


Dr Deborah Brunt is a primary care physician with a passion for women’s health + wellbeing. She would love to work with you to holistically navigate the perimenopausal life stage.

Book a consult with Dr Deb Brunt | Ōtepoti Integrative Health | Book Now

Follow on Facebook and Instagram.

Join our Meno Thrive program to optimise your health and wellbeing during perimenopause and menopause.


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