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Are you in your late 30s or 40s and feeling a profound sense of exhaustion that no amount of sleep can fix? Does a new, persistent irritability have you experiencing mood swings and snapping at loved ones? Does brain fog make it hard to concentrate on tasks that once felt effortless? Are you noticing subtle but unsettling changes like your motivation slipping, patience thinning, confidence wavering, or a sense that your body no longer responds the way it used to?
It’s easy—almost expected—to dismiss these changes as stress, burnout, parenting demands, career pressure, or simply “getting older.” As women, we are especially conditioned to normalize discomfort and push through it. But what if these experiences are not random or personal shortcomings at all? What if they are early biological signals of a major hormonal transition that medicine and culture have historically failed to explain clearly?
Our collective understanding of perimenopause—the years-long transition leading up to menopause, plus the year following your final menstrual period—is often limited to a single, iconic symptom: the hot flash. Popular media, health classes, and even many medical conversations portray menopause as something that arrives suddenly in a woman’s early 50s, announced dramatically by waves of heat, hot flashes, and night sweats.
A groundbreaking new global study published in 2026 in the journal Menopause reveals that this picture is not only incomplete but actively misleading.
Using self-reported data from more than 17,000 women in 158 countries via the Flo women’s health app, researchers uncovered a striking disconnect between what women expect perimenopause to feel like and what they actually experience. Perhaps most alarming, 33% of women aged 35 and older reported that they were unsure of their own reproductive stage—highlighting just how poorly this transition is understood.
In this article, we’ll explore the most important and counterintuitive findings from this research, explain why perimenopause so often goes unrecognized, and offer a clearer, more compassionate framework for understanding what may be happening in your body.
Ask most people to name a perimenopause symptom, and hot flashes will almost always top the list. The study confirms that this association is deeply ingrained: 71% of participants identified hot flashes as a symptom they associate with perimenopause.
But recognition and lived experience are not the same thing.
When researchers examined which symptoms women actually experienced most frequently, a very different picture emerged. Among women aged 35 and older, the most commonly reported symptoms were:
- Fatigue (83%)
- Physical and mental exhaustion (83%)
- Irritability (80%)
Hot flashes, while common, were not dominant in the early experience of perimenopause. Among women who self-identified as being in perimenopause, the numbers were even more striking:
- Physical and mental exhaustion: 95%
- Fatigue: 93%
- Irritability: 91%
In other words, exhaustion—not heat—is the defining feature of early perimenopause for most women.
This distinction matters. When symptoms don’t match expectations, we are far more likely to misinterpret what our bodies are telling us. Chronic fatigue may be blamed on poor sleep hygiene, work stress, or a lack of willpower. Irritability may be chalked up to personality changes or relationship strain. Brain fog may trigger fears about aging, competence, or even early cognitive decline!
When the hormonal context is missing, we may be prescribed antidepressants, advised to “reduce stress,” or encouraged to exercise more—interventions that may help somewhat but fail to address the root cause. Some women even leave demanding jobs or step back from responsibilities they value, believing they are no longer capable, when in reality they are navigating an unrecognized physiological transition.
If you have felt dismissed or doubted, this research offers something powerful: validation.
“While hot flashes were widely recognized (71%), women aged 35 and above reported fatigue (83%), exhaustion (83%), and irritability (80%) as the most common symptoms.”
— Menopause Journal
Why hormonal changes in perimenopause hit energy levels first
To understand why fatigue and exhaustion dominate early perimenopause, it helps to understand what’s happening hormonally. During perimenopause, estrogen and progesterone do not decline smoothly. Instead, they fluctuate—sometimes dramatically—from month to month or even day to day.
Estrogen plays a key role in mitochondrial energy production, sleep regulation, muscle recovery, and glucose metabolism. Progesterone supports restorative sleep and has calming effects on your nervous system. As these hormones become erratic during the menopause transition, energy levels often suffer long before periods stop or vasomotor symptoms like hot flashes begin.
This explains why many women say, “I don’t feel like myself anymore,” even when their menstrual cycle still appears mostly regular.
The thyroid–perimenopause connection: An overlooked hormonal overlap
One critical piece missing from many conversations about perimenopause is the thyroid. Thyroid disorders—especially hypothyroidism and Hashimoto’s disease—are far more common in women, and risk increases with age. The early stages of perimenopause often overlap with the time when thyroid dysfunction first appears or worsens.
This overlap matters because many of the most common perimenopause symptoms closely resemble symptoms of an underactive thyroid. Fatigue, brain fog, depression, weight gain, constipation, cold intolerance, dry skin, and hair thinning can all point to thyroid dysfunction—but they are also hallmarks of perimenopause.
Estrogen and thyroid hormones are deeply interconnected. Estrogen influences thyroid hormone binding and metabolism, while thyroid hormones affect mitochondrial energy production and mood regulation. As estrogen levels fluctuate during perimenopause, thyroid hormone availability can change as well, sometimes unmasking previously mild or undiagnosed hypothyroidism.
For women with existing thyroid disease, perimenopause can be a destabilizing period. Thyroid medication doses that once worked well may suddenly feel inadequate. Symptoms may intensify even when standard thyroid lab values appear “normal.”
This is one reason so many women are told their labs look fine while they feel anything but.
Clinically, this means persistent fatigue, mood changes, or cognitive symptoms during perimenopause – sometimes referred to as “peri-brain” – should not automatically be attributed to stress or aging—or even perimenopause alone. A comprehensive evaluation should consider both ovarian and thyroid hormones, especially in women with a personal or family history of thyroid disease.
Understanding this thyroid–perimenopause crossover can help women avoid years of misdiagnosis and fragmented care, and instead pursue a more integrated, hormone-informed approach.
Beyond physical exhaustion, the study highlights a profound psychological and emotional burden that has long been minimized in menopause conversations.
Among women aged 35 and older, the most frequently reported symptoms included:
- Depressive mood (77%)
- Sleep problems (76%)
- Digestive issues (76%)
- Anxiety (75%)
For women who identified as being in perimenopause, the picture became even clearer. Their top symptoms were:
- Physical and mental exhaustion (95%)
- Fatigue (93%)
- Irritability (91%)
- Sleep problems (89%)
- Depressive mood (88%)
- Brain fog (87%)
These numbers challenge the idea that emotional or cognitive symptoms are peripheral or “reactive.” Instead, they appear to be core features of the perimenopausal transition.
Estrogen influences serotonin, dopamine, and norepinephrine—neurotransmitters that regulate mood, motivation, focus, and emotional resilience. When estrogen levels fluctuate unpredictably, mood can feel unstable, anxiety may spike, and concentration can suffer.
Without a hormonal framework, many women are treated for isolated symptoms. Anxiety is addressed without discussing sleep. Depression and mood swings are treated without assessing hormonal patterns. Insomnia is managed without acknowledging its hormonal drivers. This fragmented approach can leave women feeling unseen and frustrated.
“This study shines a light on how little we still understand about perimenopause and how much it affects people’s daily lives.” — Dr. Mary Hedges, Mayo Clinic
One of the most distressing symptoms reported by women in perimenopause is brain fog. Difficulty concentrating, word-finding problems, memory lapses, and mental sluggishness can be deeply unsettling—especially for women who have built careers or identities around mental sharpness.
The study found that 87% of women in perimenopause reported brain fog, yet this symptom is rarely emphasized in mainstream menopause education.
Research suggests that estrogen supports synaptic plasticity and brain blood flow. Fluctuating estrogen levels may temporarily disrupt these processes, leading to cognitive symptoms that feel alarming but are often reversible with proper support.
Understanding this can reduce fear and self-blame, replacing them with informed advocacy.
One of the most fascinating aspects of this study is its global scope. While fatigue, exhaustion, and irritability were dominant symptoms in countries such as the United States, the United Kingdom, and Canada, other regions showed different symptom patterns.
- Digestive issues ranked among the top three symptoms in Argentina, Chile, Colombia, France, Mexico, South Africa, Nigeria, and Ireland.
- Anxiety was a top-three symptom in India.
- Sleep problems were a top-three symptom in Nigeria.
These differences suggest that cultural, dietary, environmental, and social factors may influence how symptoms are experienced, interpreted, and reported during the menopausal transition.
They also underscore the danger of one-size-fits-all menopause messaging and the importance of culturally informed care.
Beyond symptoms, the study revealed stark differences in perimenopause knowledge across countries. Women in the UK and Ireland scored highest on symptom recognition, while women in Nigeria, Venezuela, Colombia, Argentina—and notably France—had significantly lower scores.
This gap between expectation and experience has real consequences. When women do not recognize symptoms as hormonal, they delay seeking care. When clinicians are not trained to recognize early perimenopause, symptoms are dismissed or misattributed.
“Our findings highlight significant knowledge gaps, with symptoms identified as common during perimenopause differing from those most frequently experienced.”
— Menopause Journal
This landmark global study fundamentally reshapes our understanding of perimenopause. It moves the spotlight away from hot flashes alone and reveals a transition defined by fatigue, exhaustion, mood changes, sleep disruption, and cognitive strain—often beginning years earlier than women expect.
Recognizing these symptoms for what they are is not just informative—it is empowering. It allows women to advocate for themselves, seek appropriate care sooner, and release the unnecessary shame that so often accompanies midlife health changes.
Perimenopause is not a personal failure. It is a biological transition—and it’s time our conversations, research, and healthcare systems reflected that reality.
Perimenopause can be confusing, especially when so many of the symptoms overlap with thyroid issues, stress, and simply “getting older.” At Paloma, you’ll never be made to feel like you’re imagining what you’re going through or that you just have to “push through” on your own. Our care teams hear every day from women who are dealing with night sweats and hot flashes, but also with brain fog, anxiety, sleep disruption, weight changes, and a vague sense of “not feeling like myself,” and we know how disruptive that can be to work, relationships, and daily life.
If you’re living with hypothyroidism or Hashimoto’s and are now noticing cycle changes, mood shifts, or new bodily sensations you can’t quite explain, you are exactly the kind of patient who thrives with Paloma Health. Perimenopause and thyroid conditions frequently coexist, and because so many symptoms overlap—fatigue, mood changes, brain fog, weight gain—it’s easy for one to mask the other or be dismissed altogether. You deserve clinicians who understand those hormonal intersections, take your symptoms seriously, and partner with you to sort out what’s thyroid, what’s perimenopause, and what to do next.
At Paloma Health, our virtual clinic brings together convenient at-home thyroid testing, expert clinicians, hormone therapy, and ongoing support so you can get answers without endless waiting rooms or fragmented care. We combine evidence-based medicine and treatment options with nutrition and lifestyle guidance to create a plan that reflects your complete hormonal picture—not just your lab values on a single day. Many of our patients tell us that simply having a dedicated team validate their experience and explain their options is the first time they’ve felt hopeful in years.
If this article resonates with you, consider it an invitation to explore personalized care with Paloma. Tracking your symptoms, checking in on your thyroid, and talking with a clinician who understands midlife hormonal health are powerful first steps toward feeling more like yourself again. Whenever you’re ready, we’re here to help you navigate perimenopause and thyroid problems with clarity, compassion, and a plan tailored to you and your unique needs.
What are the earliest symptoms of perimenopause?
For many women, the earliest signs are fatigue, exhaustion, irritability, poor sleep, mood changes, and brain fog—often long before hot flashes appear.
Can perimenopause start in your late 30s?
Yes. Perimenopause can begin in the late 30s or early 40s, even if your periods are still regular.
Why am I so tired during perimenopause?
Fluctuating estrogen and progesterone affect energy production, sleep quality, and stress hormones, making fatigue and exhaustion very common early symptoms.
Is brain fog during perimenopause normal?
Yes. Brain fog—trouble concentrating, forgetfulness, and mental sluggishness—is a common and hormonally driven symptom, not a sign of cognitive decline.
How is perimenopause different from menopause?
Perimenopause is the transition phase leading up to menopause and can last several years; menopause is officially diagnosed after 12 months without a period.
Can perimenopause affect mental health?
Absolutely. Hormonal fluctuations can trigger anxiety, low mood, irritability, and sleep problems, even in women with no prior mental health history.
How is the thyroid connected to perimenopause symptoms?
Thyroid dysfunction and perimenopause share many symptoms, and estrogen fluctuations can affect thyroid hormone availability—sometimes worsening or unmasking thyroid issues.
When should I talk to a doctor about possible perimenopause?
If you’re over 35 and experiencing persistent fatigue, mood changes, brain fog, or sleep problems that don’t make sense for you, it’s worth starting the conversation—and asking about both hormonal and thyroid evaluation.
understand the connection
Perimenopause, Menopause, and Hypothyroidism
Gain insights into how these conditions are linked and how to manage your health effectively.
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