Post Menstrual Syndrome: Why You Feel Worse AfterYour Period (And What You Can Do About It)
- Michaela Newsom
- 6 days ago
- 15 min read
KEY TAKEAWAYS
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TABLE OF CONTENTS
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What is Post Menstrual Syndrome?
Many women expect to feel better once their period starts. After all, premenstrual syndrome (PMS) is supposed to disappear when bleeding begins, yet for some women, the opposite happens.
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The cramps may settle, but they're left feeling exhausted, flat, anxious, emotionally fragile or unable to think clearly. They struggle to get through the working day, lose motivation to exercise and find themselves wondering why they feel so unlike themselves when their period is already over.
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This collection of symptoms has become known as post menstrual syndrome (PoMS). Although it is increasingly recognised by clinicians working in women's health and discussed widely by women experiencing these symptoms, post menstrual syndrome is not currently recognised as an official medical diagnosis and there are no established diagnostic criteria.
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Instead, it describes a pattern of symptoms that typically occur:
during menstruation
immediately after bleeding ends
throughout the first few days of the follicular phase
Rather than being caused by one single hormone, post menstrual syndrome appears to reflect the interaction between hormonal withdrawal, inflammation, iron status, stress physiology and the body's ability to produce energy efficiently. That means the symptoms are very real—but the reasons behind them are often more complex than simply "low oestrogen."
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Post Menstrual Syndrome vs Premenstrual Syndrome
Although there is some overlap between the symptoms of premenstrual syndrome and post menstrual syndrome, PoMS is not simply ‘PMS but later’. Although both are driven by changes in ovarian hormones, the underlying mechanisms are different and they occur in different hormonal and metabolic environments.
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PMS occurs in the late luteal phase when oestrogen and progesterone are falling and symptoms usually improve when menstruation begins. It is believed that it is the changing hormone levels that triggers symptoms.
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PoMS occurs in the early follicular phase when oestrogen and progesterone are at their lowest and symptoms usually begin or worsen when menstruation starts. During this phase energy demand is higher as the endometrium is regenerated but iron availability may be at its lowest and impact energy production.
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Is Post Menstrual Syndrome a Real Condition?
At present, scientific research specifically examining post menstrual syndrome is limited. However, there is strong evidence that the early follicular phase represents one of the lowest-energy hormonal environments of the menstrual cycle.
Both oestrogen and progesterone are low, blood loss has just occurred and iron availability may be temporarily reduced whilst inflammatory mediators remain elevated.
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For women who are already under significant physiological stress, this combination may be enough to expose underlying imbalances that were previously being compensated for. From a functional medicine perspective, menstruation can be thought of as a physiological stress test. If your body has limited reserves, your symptoms are often most noticeable when hormones are at their lowest.
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Common Symptoms of Post Menstrual Syndrome
Symptoms vary considerably between individuals but may include:
Extreme fatigue
Brain fog
Difficulty concentrating
Anxiety
Low mood
Irritability
Reduced motivation
Muscle weakness
Poor exercise recovery
Headaches
Dizziness
Light-headedness
Food cravings
Low libido
Poor sleep
Digestive discomfort
Feeling overwhelmed
For some women these symptoms last only one or two days. For others they may continue throughout much of the follicular phase.
Why Do Symptoms Occur After Your Period?
One of the biggest misconceptions about female hormones is that symptoms are caused solely by declining oestrogen. Several physiological systems change simultaneously during and immediately after menstruation.
Oestrogen is at its lowest
Progesterone has disappeared
Iron loss can reduce oxygen delivery
Inflammation levels are elevated
Sugar cravings can destabiliste blood sugar levels
Stress hormones can amplify symptoms
Histamine may be a contributing factor
Mitochondria may be less efficient
Oestrogen Is at Its Lowest
Oestrogen does far more than regulate reproduction. It also influences:
mitochondrial energy production
glucose metabolism
serotonin production
dopamine signalling
blood vessel function
muscle recovery
brain plasticity
autonomic nervous system regulation
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During the early follicular phase, oestrogen reaches its lowest concentration.
For some women, this temporary hormonal low point translates into reduced physical and mental energy. Research suggests oestrogen supports mitochondrial biogenesis and ATP production, meaning lower levels may reduce cellular energy efficiency until oestrogen begins to rise again. This explains why some women describe feeling as though someone has "pulled the plug" on their energy immediately after their period.
Progesterone Has Also Disappeared
Much attention is given to falling oestrogen, but progesterone has also dropped dramatically. Progesterone influences:
GABA activity
sleep quality
nervous system regulation
anxiety resilience
When progesterone falls, the calming influence it exerts on the brain is temporarily lost. Women who are already experiencing chronic stress may therefore feel especially anxious or emotionally fragile immediately after menstruation.
Iron Loss Can Reduce Oxygen Delivery
Even relatively modest menstrual blood loss removes iron from the body. Iron is essential for:
haemoglobin production
oxygen transport
mitochondrial respiration
ATP synthesis
If iron stores are already marginal, menstruation may temporarily reduce oxygen delivery to tissues, contributing to fatigue, dizziness and reduced exercise capacity.
Inflammation Doesn't Stop When Bleeding Starts
Inflammatory prostaglandins help initiate menstruation and levels are high during menstruation. While they are essential for normal uterine function, they can also contribute to:
headaches
fatigue
pain
digestive symptoms
reduced mood
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Some women also show higher circulating inflammatory cytokines around menstruation, particularly if they have conditions such as endometriosis, adenomyosis or autoimmune disease.
Blood Sugar Regulation Becomes More Important
When energy production is reduced, the brain often compensates by increasing its demand for glucose. This may explain why many women experience:
sugar cravings
shakiness
poor concentration
afternoon crashes
If insulin resistance or blood glucose instability already exists, symptoms can become considerably more noticeable during this phase of the cycle.
Stress Hormones Can Magnify Symptoms
The menstrual cycle places additional demands on the body. For women already living with chronic stress, burnout or poor sleep, menstruation can expose reduced resilience.
The hypothalamic-pituitary-adrenal (HPA) axis and the hypothalamic-pituitary-ovarian (HPO) axis communicate constantly. Disruption in one system often influences the other. This means post menstrual fatigue is frequently more pronounced in women experiencing chronic psychological stress, caring responsibilities, overtraining or insufficient recovery.
Histamine May Play a Role
Oestrogen and histamine have a bidirectional relationship. Histamine can stimulate oestrogen release, while oestrogen can influence mast cell activity.
Although histamine-related symptoms are more commonly discussed around ovulation when oestrogen peaks, some women with mast cell activation or histamine intolerance appear to experience worsening headaches, dizziness or fatigue around menstruation, suggesting inflammatory pathways may remain active beyond the onset of bleeding.
Mitochondria May Be Under Greater Pressure
Perhaps the most useful way to understand post menstrual syndrome is to think about energy availability and during menstruation a number of factors impact how much energy is available.
Hormones regulate how efficiently mitochondria generate ATP and during menstruation they are at their lowest.
Inflammation increases energy demand and there is a rise in inflammatory prostaglandins at this time to trigger menstruation.
Iron supports oxygen transport and blood loss during menstruation can reduce iron availability.
Stress increases energy expenditure and poor sleep limits mitochondrial recovery.
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When several of these factors occur simultaneously, the result can feel like running a marathon with a half-charged battery. When supporting PoMS, the goal isn't simply to "balance hormones"—it's to improve the body's capacity to generate energy and recover throughout the entire menstrual cycle.
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Who Is More Likely to Experience Post Menstrual Syndrome?
While almost every woman experiences hormonal fluctuations throughout the menstrual cycle, not everyone develops symptoms after their period. This suggests that hormonal changes most likely the trigger rather than the root cause. The hormonal shifts of the menstrual cycle place additional demands on the body's systems. If those systems are already under strain—whether through chronic stress, nutrient deficiencies, inflammation or metabolic dysfunction—symptoms are much more likely to appear.
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Women who may be more susceptible to post menstrual syndrome include those with:
Heavy menstrual bleeding
Low iron stores or iron deficiency
Perimenopause
Endometriosis or adenomyosis
Polycystic ovary syndrome (PCOS)
Thyroid dysfunction
Chronic stress or burnout
Long COVID or post-viral fatigue
Chronic inflammatory conditions
Autoimmune disease
Histamine intolerance or mast cell activation syndrome (MCAS)
Poor sleep
Relative Energy Deficiency in Sport (RED-S)
Poor dietary intake or restrictive eating patterns
The encouraging news is that many of these factors are modifiable. Rather than accepting fatigue and brain fog as an inevitable part of your cycle, identifying and addressing the underlying drivers can often make a significant difference.
Why is the body struggling to adapt to what should be a normal physiological event?
Instead of focusing solely on reproductive hormones, we need to consider the systems that influence how resilient your body is to hormonal change.
These include:
Cellular energy production
Blood sugar regulation
Nutrient status
Inflammation
Thyroid function
Gut health
Stress physiology
Liver detoxification
Sleep quality
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1. Supporting Cellular Energy Production
One of the most consistent themes in women with post menstrual syndrome is fatigue. While it's tempting to assume this is simply due to blood loss, fatigue is usually much more complex than that.
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Every cell in your body relies on tiny structures called mitochondria to produce ATP, the energy currency that powers everything from muscle contraction to memory formation.
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Oestrogen plays an important role in maintaining mitochondrial function. It supports:
Mitochondrial biogenesis (the creation of new mitochondria)
Antioxidant defence
Efficient glucose metabolism
Fat oxidation
ATP production
When oestrogen is at its lowest, mitochondrial efficiency may temporarily decline. For women whose mitochondria are already under pressure—from poor sleep, nutrient deficiencies, chronic inflammation or persistent stress—this temporary dip can be enough to produce significant fatigue.
2. Optimising Iron Status
Iron deserves particular attention because menstruation is the leading cause of iron loss in premenopausal women. Iron is involved in:
Oxygen transport
ATP production
Cognitive performance
Dopamine synthesis
Thyroid hormone metabolism
Muscle function
Many women are told their iron levels are "normal", yet continue to experience symptoms consistent with suboptimal iron status. This is partly because laboratory reference ranges are designed to identify disease rather than optimal physiological function. For example, ferritin may fall comfortably within the reference range while still being insufficient to support energy production, particularly in women who menstruate heavily.
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It's also important to remember that ferritin is an acute-phase protein, meaning it rises during inflammation. A normal—or even elevated—ferritin result doesn't always reflect adequate iron stores if inflammatory markers are also raised.
For this reason, iron status is best interpreted using a broader picture, including:
Ferritin
Haemoglobin
Mean cell volume (MCV)
Mean cell haemoglobin (MCH)
Transferrin saturation
Serum iron
Total iron binding capacity (TIBC)
Soluble transferrin receptor (where available)
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Rather than supplementing iron indiscriminately, identifying the underlying cause of low iron—whether heavy menstrual bleeding, poor absorption or gastrointestinal blood loss—is equally important.
3. Stabilising Blood Sugar
Have you ever noticed that you're far more likely to crave sugar after your period?
This isn't simply a lack of self-control. Your brain consumes around 20% of the body's energy despite accounting for only 2% of body weight. When cellular energy production is less efficient, maintaining a steady supply of glucose becomes even more important. Rapid swings in blood glucose can contribute to:
Brain fog
Fatigue
Anxiety
Irritability
Headaches
Cravings
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For women experiencing post menstrual syndrome, one of the most effective nutritional strategies is often surprisingly simple: Build meals that provide stable energy rather than quick bursts of fuel.
This means prioritising:
Protein at every meal
Fibre-rich vegetables
Healthy fats
Slow-release carbohydrates
Regular meal timing
Many women notice a significant improvement in afternoon energy simply by eating a protein-rich breakfast instead of relying on coffee to carry them through the morning.
4. Reducing Chronic Inflammation
Inflammation is an essential part of the menstrual cycle. Without inflammatory signalling, menstruation could not occur. The problem arises when inflammation remains chronically elevated throughout the rest of the month. Persistent low-grade inflammation increases energy requirements and may contribute to:
Fatigue
Low mood
Pain sensitivity
Brain fog
Poor recovery
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Dietary patterns rich in colourful vegetables, extra virgin olive oil, oily fish, herbs, spices and polyphenol-rich foods are consistently associated with lower inflammatory markers. Equally important is identifying the source of inflammation.
This may include:
Poor oral health
Chronic infections
Food intolerances (where clinically appropriate)
Poor sleep
Obesity
Sedentary behaviour
Chronic psychological stress
Endometriosis
Autoimmune disease
5. Thyroid Health
Fatigue after your period isn't always hormonal. Sometimes the menstrual cycle simply reveals an underlying thyroid issue.
Thyroid hormones regulate:
Basal metabolic rate
Heat production
Mitochondrial function
Muscle strength
Cognitive function
Menstrual regularity
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Symptoms of suboptimal thyroid function—including fatigue, brain fog, constipation, dry skin and low mood—often overlap with post menstrual syndrome.
Rather than relying solely on TSH, a comprehensive thyroid assessment may include:
TSH
Free T4
Free T3
Thyroid peroxidase antibodies (TPO)
Thyroglobulin antibodies
Reverse T3 (where clinically appropriate)
Nutrients such as selenium, iodine (where appropriate), zinc, iron and vitamin A also play important roles in thyroid hormone production and activation.
6. Understanding the Stress Response
The hormonal flow of the menstrual cycle interacts continuously with your nervous system. Periods of prolonged stress can reduce the body's capacity to adapt to hormonal fluctuations through changes in the hypothalamic-pituitary-adrenal (HPA) axis. Many women with post menstrual syndrome describe:
Feeling "wired but tired"
Waking during the night
Needing caffeine to function
Feeling exhausted but unable to relax
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These symptoms often reflect changes in stress physiology, circadian rhythm and autonomic nervous system regulation. Whilst adaptogenic herbs can be useful, supporting the stress response requires creating the conditions in which the nervous system can recover.
These include:
Consistent sleep and wake times
Morning daylight exposure
Regular movement
Blood sugar stability
Relaxation practices
Appropriate exercise recovery
Time spent in nature
Meaningful social connection
7. Supporting Gut Health
The gut plays a surprisingly important role in hormonal health. It influences:
Nutrient absorption
Iron uptake
B-vitamin production
Immune regulation
Inflammation
Oestrogen metabolism
Digestive symptoms are common in women experiencing post menstrual syndrome, particularly if there is underlying IBS, coeliac disease, inflammatory bowel disease or dysbiosis.
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Where digestive symptoms coexist with fatigue, recurrent nutrient deficiencies or inflammatory symptoms, investigating gut health may provide valuable answers.
Supporting the gut often begins with the fundamentals:
Eating sufficient fibre
Including fermented foods where tolerated
Chewing thoroughly
Managing stress during meals
Addressing constipation
Identifying underlying gastrointestinal conditions where appropriate
Functional Testing: Looking Beneath the Surface
One of the strengths of functional medicine is using targeted testing to understand why symptoms are occurring, rather than simply confirming that they exist.
Testing should always be guided by symptoms and clinical history, but depending on the individual, the following investigations may be helpful:
Comprehensive blood testing including a full blood count, iron panel, full thyroid panel, nutrient status, metabolic health and inflammatory markers
Hormone testing including oestrogen, progesterone, LH, FSH, Testosterone, SHBG, DHEA-S and prolactin.
Hormone testing is not necessary for every woman experiencing post menstrual syndrome, particularly if she has regular cycles. However, in women with irregular periods, suspected perimenopause or symptoms suggestive of ovulatory dysfunction, it can help build a clearer clinical picture.
Nutrition and Lifestyle Strategies for Post Menstrual Syndrome
One of the most empowering aspects of understanding post menstrual syndrome is recognising that there is rarely a single "magic bullet". Instead, improvements often come from supporting the body's natural resilience across multiple systems.
The aim isn't to eliminate hormonal fluctuations—they're a normal part of a healthy menstrual cycle. Rather, it's to improve your body's ability to adapt to those fluctuations so they no longer leave you feeling exhausted, anxious or overwhelmed.
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Build Every Meal Around Protein
Following menstruation, your body enters a phase of rebuilding.
Protein provides the amino acids required for tissue repair, neurotransmitter production, immune function and muscle maintenance. It also helps stabilise blood glucose, reducing the energy crashes and cravings that many women experience during the early follicular phase.
Aim for 25–35 g of high-quality protein at each meal, with a particular focus on breakfast.
Good choices include:
Eggs
Greek yoghurt or skyr
Cottage cheese
Fish
Poultry
Lean meat
Tofu or tempeh
Lentils and beans (combined with wholegrains where appropriate)
Spreading protein intake evenly across the day appears to support muscle protein synthesis more effectively than consuming most protein at dinner.
Replenish Iron Naturally
If your periods are heavy, iron-rich foods become especially important.
Excellent dietary sources include:
Lean red meat
Liver (if appropriate)
Mussels and oysters
Sardines
Lentils
Chickpeas
Pumpkin seeds
Spinach
Tofu
Remember that plant-based (non-haem) iron is absorbed less efficiently than animal-derived iron. Pairing plant sources with foods rich in vitamin C—such as peppers, kiwi fruit, citrus fruits or berries—can significantly improve absorption. Conversely, tea and coffee consumed with meals may reduce iron absorption and are best enjoyed between meals if iron deficiency is a concern.
Focus on Anti-Inflammatory Foods
Inflammation is a normal part of menstruation, but reducing chronic background inflammation may improve recovery afterwards. An anti-inflammatory dietary pattern is consistently associated with better metabolic health and lower inflammatory markers.
Aim to include:
Colourful vegetables
Berries
Herbs and spices
Extra virgin olive oil
Oily fish
Nuts
Seeds
Legumes
Wholegrains
Polyphenols found in foods such as blueberries, cocoa, green tea and pomegranate also appear to support mitochondrial function and antioxidant defence.
Prioritise Sleep During Your Recovery Window
The first few days after menstruation are an ideal time to support recovery.
Sleep is when many of the body's repair processes occur. Aim for:
7.5–9 hours of sleep
Consistent sleep and wake times
Morning daylight exposure
Limiting bright screens before bed
A cool, dark bedroom
If sleep is consistently poor, addressing this may have a greater impact on symptoms than adding multiple supplements.
Match Exercise to Your Energy Levels
Many women feel guilty if they don't exercise intensely every day. However, your body isn't designed to perform at exactly the same level throughout the menstrual cycle. If fatigue is prominent after your period, consider temporarily reducing training intensity while prioritising:
Walking
Mobility work
Pilates
Yoga
Light resistance training
Zone 2 cardiovascular exercise
As oestrogen rises through the follicular phase, many women naturally notice improvements in strength, motivation and exercise capacity. Learning to work with your physiology rather than against it often leads to better long-term progress.
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When Should You Seek Medical Advice?
Although feeling slightly tired during or after your period can be normal, persistent or severe symptoms should never be dismissed.
Arrange an appointment with your GP or healthcare practitioner if you experience:
Fatigue that interferes with daily life every month
Heavy menstrual bleeding (for example, soaking through pads or tampons every hour or passing large clots)
Dizziness or fainting
New or worsening headaches
Persistent low mood or anxiety
Breathlessness
Significant weight changes
Very irregular periods
Bleeding between periods
Symptoms that continue for most of the month
These symptoms may indicate conditions such as iron deficiency anaemia, thyroid disease, endometriosis, adenomyosis or other underlying health issues that warrant investigation.
Final Thoughts
Although post menstrual syndrome is not yet recognised as a formal medical diagnosis, it reflects a pattern that many women experience and that makes physiological sense. The early follicular phase is a time of low ovarian hormones, recovery from menstrual blood loss and increased demands on the body's energy systems.
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Rather than viewing these symptoms as a sign that your body is failing, think of them as valuable feedback. They may be highlighting areas where your physiology needs additional support—whether that's improving iron status, stabilising blood sugar, reducing inflammation, optimising thyroid function or restoring resilience after prolonged stress.
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Frequently Asked Questions
Is post menstrual syndrome a recognised medical condition?
Not currently. Post menstrual syndrome is an emerging clinical term used to describe symptoms that occur during or shortly after menstruation. While there are no formal diagnostic criteria at present, the symptoms experienced by many women are real and supported by our understanding of hormonal physiology, inflammation and energy metabolism.
Why do I feel worse after my period than before it?
For some women, the early follicular phase represents the point at which oestrogen and progesterone are at their lowest. Combined with menstrual blood loss, inflammation and existing physiological stress, this can result in fatigue, brain fog, headaches or low mood.
Can low iron cause post menstrual fatigue?
Yes. Menstruation is the leading cause of iron loss in premenopausal women. Low iron stores can impair oxygen delivery and mitochondrial energy production, contributing to fatigue and reduced exercise tolerance. However, iron deficiency is only one of several possible contributors and should be confirmed with appropriate testing before supplementation.
Does post menstrual syndrome get worse during perimenopause?
It can. Hormonal fluctuations become more pronounced during perimenopause, and ovulation becomes less predictable. This may increase the likelihood of both premenstrual and post menstrual symptoms, although every woman's experience is different.
Should I take supplements every month?
Not necessarily. Supplements should be tailored to your individual needs, symptoms and blood test results. A balanced diet, good sleep, stress management and regular physical activity remain the foundations of long-term health.
Can stress make post menstrual syndrome worse?
Absolutely. Chronic stress affects the hypothalamic-pituitary-adrenal (HPA) axis, sleep quality, inflammation and blood glucose regulation. These changes can reduce your ability to adapt to the hormonal fluctuations that occur during the menstrual cycle.
Author's note:Â Post menstrual syndrome is an emerging clinical concept rather than a formally recognised medical diagnosis. The recommendations in this article are based on current evidence relating to menstrual physiology, hormonal regulation, energy metabolism and nutritional medicine, combined with clinical experience in supporting women with cyclical symptoms. If your symptoms are severe, persistent or worsening, please seek assessment from your GP or a qualified healthcare professional to exclude underlying medical conditions.
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References & Further Reading
Reed BG, Carr BR. The Normal Menstrual Cycle and the Control of Ovulation. Endotext. 2023.
Hall JE. Guyton and Hall Textbook of Medical Physiology. 15th ed. Elsevier; 2024.
Prior JC. Progesterone for symptomatic perimenopause. Climacteric. 2018;21(4):358–365.
Rettberg JR, Yao J, Brinton RD. Estrogen: a master regulator of bioenergetic systems in the brain. Brain Research.2014;1379:34–47.
Ventura-Clapier R, et al. Estrogens, estrogen receptors and cardiac mitochondrial function. Cardiovascular Research. 2017;113:711–720.
Arnold AP, et al. Sex hormones and mitochondrial function. Cell Metabolism. 2022;34:1463–1479.
Camaschella C. Iron deficiency. New England Journal of Medicine. 2015;372:1832–1843.
Muñoz M, et al. Iron deficiency without anaemia. The Lancet Haematology. 2021;8:e657–e668.
Tolkien Z, et al. Ferrous sulfate supplementation causes significant gastrointestinal side effects in adults. PLoS One.2015;10:e0117383.
Maybin JA, Critchley HOD. Menstrual physiology. Physiological Reviews. 2015;95:1149–1179.
Evans J, Salamonsen LA. Inflammation and menstruation. Journal of Reproductive Immunology. 2012;97:70–75.
American Diabetes Association. Standards of Care in Diabetes. 2025.
Clegg DJ. Minireview: Sex hormones and metabolic regulation. Endocrinology. 2012;153:2547–2552.
Taylor PN, et al. Global epidemiology of thyroid disorders. Lancet Diabetes & Endocrinology. 2018.
NICE Guideline NG145. Thyroid Disease: Assessment and Management. 2019 (updated).
About The Author
Michaela Newsom
Registered Nutritional Therapist, mBANT, rCNHC
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Michaela is a women’s health expert with a specialist interest in the impact of menopause on the female brain. Her mission is to empower women to optimise their cognitive function and mental wellbeing throughout life with a special focus on the challenges that take place during perimenopause, menopause and beyond.
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With a Postgraduate qualification in Personalised Nutrition and advanced Functional medicine training with IFM and the Kharrizian Institute Michaela has expertise spanning hormones, brain health, cognitive function and mood disorders.