One day you’re getting on with life as usual. Then slowly you start noticing that you’re forgetting words mid-sentence, waking at 3am, snapping at the smallest things, noticing your jeans fit differently and wondering why your knees have started creaking. 

Individually, these changes are easy to blame on stress, ageing or simply having too much on your plate. But when several start happening at once, you might begin joining the dots: could this be perimenopause?

The answer may lie in changes happening far beyond your periods. Understanding what perimenopause can do throughout your body can make those seemingly random symptoms feel a lot less random - and help you know where to start supporting yourself.¹ ²

What actually happens during perimenopause?

Perimenopause is the transition leading up to menopause. As the ovaries gradually change the way they function, ovulation becomes less predictable and levels of hormones including oestrogen and progesterone can become much more variable. Eventually, oestrogen levels settle at a lower level and periods stop altogether.¹ ³

That matters because these hormones are not only involved in reproduction.

Oestrogen receptors are found in tissues throughout the body, while oestrogen and progesterone interact with systems involved in brain function, bone, muscle, metabolism, blood vessels, skin and more. This helps explain why perimenopause symptoms can show up from head to toe - and why two women may experience the transition very differently.² ⁴

It is also why perimenopause is rarely as simple as “your oestrogen is low”.

Particularly during the earlier stages, hormones can fluctuate considerably. You might therefore have weeks when you feel completely like yourself followed by periods when your sleep, mood, cycle or energy suddenly feel very different.

Your brain: mood, memory and brain fog

Ever walked into a room and forgotten why you went there? Lost a perfectly ordinary word halfway through a sentence? Or found yourself reacting far more strongly to something you would once have brushed off?

Perimenopause brain fog, forgetfulness, mood swings, anxiety and low mood are all recognised symptoms of the menopause transition.¹ 

One reason may be the relationship between oestrogen and the brain. Oestradiol interacts with neurotransmitter systems including serotonin, which is involved in mood, and can also influence brain regions involved in memory and cognition. Research suggests that cognitive changes during the menopause transition are usually subtle, but difficulties with memory and concentration are commonly reported.⁴ ⁵

And it isn't necessarily simply about having “less” oestrogen. The variability of reproductive hormones during perimenopause may matter too, with some women appearing more sensitive to hormonal change than others.

Sleep also feeds into the picture: being chronically tired can make concentration, memory and emotional regulation feel harder still.¹

Your sleep and nervous system: why you can feel tired but wired

One of the most frustrating perimenopause symptoms is feeling exhausted all day - only to find your brain fully awake when your head finally hits the pillow.

Sleep disturbance is common during the menopause transition. You may struggle to fall asleep, wake repeatedly during the night or wake earlier than you want to. Hot flushes and night sweats can contribute, but they are not the whole story.¹ ⁷

Progesterone is also a neuroactive hormone. One of its metabolites, allopregnanolone, interacts with GABA receptors in the brain. GABA is involved in reducing nervous-system activity and regulating sleep and feelings of calm. As ovulation becomes less predictable during perimenopause, progesterone patterns change too, although the relationship between hormones and sleep is complex and still being studied.⁸

Poor sleep can then create a knock-on effect: perimenopause fatigue, irritability, poorer concentration and lower stress tolerance can all feel worse after several disrupted nights.¹

Your muscles: why strength starts to matter more

If workouts suddenly seem harder, recovery takes longer or you simply don't feel as strong as you used to, hormones may be one part of the picture.

Skeletal muscle contains oestrogen receptors, and oestradiol appears to have roles in muscle maintenance, repair and the function of the satellite cells involved in regenerating muscle tissue. Across the menopause transition and with ageing, women can experience changes in muscle mass, quality and strength.⁹

Ageing, activity levels, diet, sleep and other factors all contribute too, so every change in strength cannot be blamed on hormones. But menopause is a useful point to become more intentional about maintaining muscle.

And that matters for far more than how toned you feel. Muscle supports mobility, bone health, metabolic health and your ability to stay strong as you get older.

Your bones and joints: changes you may not be able to see

Bone is constantly being broken down and rebuilt.

Oestrogen helps regulate this process. As oestrogen levels decline around menopause, the balance can shift towards greater bone loss, which is why lower oestrogen after menopause is associated with reduced bone density and an increased risk of osteoporosis over time.² ¹¹

You may not feel bone loss happening, but you might notice other musculoskeletal changes. Joint aches, muscle pain and stiffness are recognised menopause-associated symptoms, although joint pain has many possible causes and should not automatically be assumed to be hormonal.¹ ²

This is one reason thinking about bone health before menopause matters.

Your metabolism and body composition: when your body starts storing fat differently

If your body suddenly seems to be changing shape despite your routine staying much the same, you're not imagining the possibility of a shift.

Perimenopause weight gain and changes in body composition are common concerns, but the science is more nuanced than “menopause slows your metabolism”.¹

Ageing itself can influence weight and muscle mass. At the same time, the menopause transition appears to be associated with changes in where fat is stored, with a greater tendency towards abdominal or visceral fat. Hormonal changes may also interact with glucose metabolism, lipids and insulin sensitivity.¹³

Loss of muscle can matter here too. Muscle is metabolically active tissue, so protecting it becomes increasingly important as we move through midlife.

Instead of focusing purely on the number on the scales, think about body composition: maintaining muscle, supporting metabolic health and nourishing your body well.

Your heart and cholesterol: changes worth thinking about now

Your hormones interact with your cardiovascular system too.

Across the menopause transition, changes can occur in blood lipids, blood pressure, vascular function, glucose regulation and body-fat distribution. Oestrogen has effects on blood vessels and lipid metabolism, although cardiovascular risk is influenced by many factors including age, genetics, smoking, diet and physical activity.¹³ ¹⁴

You may also notice heart palpitations - feeling as though your heart is pounding, fluttering or beating differently - which the NHS recognises as a possible menopause symptom.¹

Palpitations can have many other causes, however, so new or concerning heart symptoms should be discussed with a healthcare professional rather than automatically attributed to perimenopause.

Your skin: why it may suddenly feel drier

Skin is another oestrogen-responsive tissue.

Research suggests oestrogen has roles in collagen production, skin thickness, elasticity and hydration. As oestrogen falls, some women notice that their skin becomes drier, thinner or less elastic. Dry or itchy skin is also included among recognised menopause symptoms.¹ ¹⁵

Of course, hormones are only one part of skin ageing. Sun exposure, genetics, smoking, environment and your existing skincare routine all matter too.

But if the moisturiser you've used for years suddenly doesn't seem enough, hormonal change could be another piece of the puzzle.

Your cycle: often the clue that joins everything together

Periods don't necessarily just become gradually lighter and then disappear.

As ovarian function changes, ovulation becomes less consistent and hormone patterns become less predictable. Your cycles may get shorter, longer or more irregular. Bleeding can become heavier or lighter, and symptoms that feel like PMS may change too.¹ ³

For many women, changing periods are one of the first obvious signs of perimenopause.

For others, the brain fog, poor sleep, anxiety or aching joints appear first - which is why it can take time to make the connection.

Seeing those symptoms alongside your cycle can sometimes make the pattern much clearer.

So, what does perimenopause actually feel like?

There isn't one universal perimenopause experience.

You might notice your periods first. Someone else may notice sleep. Another woman may simply realise that she feels more anxious, forgetful, exhausted or less like herself than she used to.

What matters is recognising that these changes do not always happen independently.

Your hormones interact with systems throughout your body. Sleep can affect mood. Muscle can affect metabolism. Night sweats can affect sleep. Changing cycles can help you spot a pattern that previously looked like a collection of completely unrelated symptoms.

That is why understanding what happens during perimenopause can be so useful.

Not because every headache, bad night or aching knee after 35 means hormones are responsible - they aren't.

But because knowing what can change gives you another piece of information to work with.

And sometimes, joining those dots is the first step towards getting the right support.

If you're experiencing menopause or perimenopause symptoms that are bothering you, or you're unsure whether the changes you're noticing could have another cause, speak to your GP or another healthcare professional. NICE recommends discussing symptoms, health needs and available treatment options on an individual basis.²

References

1. NHS. Symptoms of menopause and perimenopause. Updated 2026. NHS: Symptoms of menopause and perimenopause

2. National Institute for Health and Care Excellence (NICE). Menopause: identification and management (NG23). Updated guidance. NICE NG23 recommendations

3. Maki PM, Freeman EW, Greendale GA, et al. Cognition and mood in perimenopause: a systematic review and meta-analysis. J Steroid Biochem Mol Biol. 2014;142:90–98. Read the paper via PubMed Central

4. Russell JK, Jones CK, Newhouse PA. The role of estrogen in brain and cognitive aging. Neurotherapeutics. 2019. Read the review

5. Greendale GA, Derby CA, Maki PM. Perimenopause and cognition. Obstet Gynecol Clin North Am. 2011. Read the review

6. NHS. Things you can do to help menopause and perimenopause symptoms. Updated 2026. NHS menopause self-care guidance

7. Women's Health Concern / British Menopause Society. Understanding and managing sleep problems during the menopause. 2025. Women's Health Concern sleep guidance

8. Sleep Disturbance and Perimenopause: A Narrative Review. 2025. Read the review via PubMed Central

9. Geraci A, Calvani R, Ferri E, et al. Sarcopenia and Menopause: The Role of Estradiol. Front Endocrinol. 2021. Read the review

10. NHS. Physical activity guidelines for adults aged 19 to 64. NHS physical activity guidance

11. Women's Health Concern / British Menopause Society. Osteoporosis factsheet. Women's Health Concern osteoporosis factsheet

12. NHS. Vitamin D. NHS vitamin D guidance

13. Marlatt KL, Beyl RA, Redman LM. Body composition and cardiometabolic health across the menopause transition. Obesity. 2022. Read the review

14. Cardiovascular Risk Associated with Menopause and Menopause Hormone Therapy: A Review and Contemporary Approach to Risk Assessment. 2025. Read the review

15. Lephart ED. Factors Influencing Skin Aging and the Important Role of Estrogens and Selective Estrogen Receptor Modulators. Clin Cosmet Investig Dermatol. 2022. Read the review

16. NHS. Emollients. NHS emollient guidance