Perimenopause: What It Is, When It Starts, and Why It Gets Missed
Most women learn about menopause, and most think it is the full transition period a woman’s body goes through later in life. As my body started changing I assumed it was part of the “menopause” transition. I would soon learn there’s a whole different classification for the years leading up to what is actually menopause. This stretch of time can last a decade or more, produce dozens of symptoms, and oftentimes includes a conversation with a doctor saying your bloodwork looks normal. Perimenopause is one of the most common experiences in women’s health and one of the most reliably misidentified. Understanding what is actually happening hormonally explains both why the symptoms are so strange and why they are so often missed.
What perimenopause actually is
Here’s the part that surprised me most: menopause is actually a single day.
It gets diagnosed backwards — twelve months after your final period, you find out you reached menopause a year ago. Everything before that day, all of it, is perimenopause. So when we say “menopause symptoms,” we are almost always talking about perimenopause. However, I will say, many women experience symptoms after their one “menopause” day that can be very debilitating as well.
Women have three (yes, you heard me right — 3) primary hormones that influence the way we feel, function, and process. Everyone knows about estrogen and progesterone. The one that shocked me is testosterone. Women produce it too, in meaningful amounts, and almost nobody checks it or talks about it, and the effects are just as important.
So let’s look at what happens to all three hormones as we move through perimenopause.
Estrogen: not a slow decline
From what I had always heard, perimenopause happens because your estrogen slowly declines. Simple… but not really what happens.
In the early years of perimenopause, estrogen doesn’t decline steadily. It gets erratic. Researchers looking at this stage have argued we should drop the “slow decline” model altogether, because what actually shows up is erratically higher estradiol — not consistently low. About a third of perimenopausal cycles contain what’s called a luteal out-of-phase event (LOOP): a second surge of estrogen arriving during the second half of the cycle, when levels should be settling down. Those surges can push estrogen well above where it sat in your thirties.¹
Progesterone: the one that actually drops
Progesterone is the hormone that genuinely declines, and it drops earlier and more reliably than estrogen, as ovulation gets inconsistent. The waking at 2 or 3 in the morning and lying there wide awake, anxiety and irritability that don’t match anything actually going on in your life, periods that turn heavy and long, or spotting for days before they start, breast tenderness, bloating, PMS that shows up earlier in the cycle and hits harder than it used to, migraines clustering around your period…those are all thanks to declining progesterone.
Essentially picture progesterone like a dimmer switch and estrogen more like a light that flickers hard before it goes out. Bringing with them their own variety of misery. The inconsistency in their levels is where the term “estrogen dominance” comes into play — too much estrogen in proportion to progesterone (more on that in a minute) — and it also comes with its own mix of frustrating symptoms.
Testosterone: the one on its own schedule
I have learned SO much about testosterone specifically as it relates to women and the myriad of things it brings to the table. It has been a fascinating education in how women’s bodies actually work — a lesson I wish every woman knew.
After I realized women produce testosterone in any meaningful amount, I assumed it must drop during perimenopause along with everything else. It does drop — about 25% between age 40 and the late fifties. But it isn’t perimenopause doing it and makes everything else worse especially if you didn’t have a lot to begin with. There was a 2026 study of roughly 1,100 women between 40 and 69 found that decline happened at the same rate whether a woman was premenopausal, perimenopausal, or postmenopausal.⁵
Testosterone isn’t following the perimenopause script. It’s on a slow, steady age decline that started back in your twenties and just keeps going, completely indifferent to what your cycles are doing.
Which means if you’re in your late forties feeling the effects of lower testosterone — and it contributes to muscle maintenance, bone, energy, and libido — that’s not perimenopause doing it – it’s just terrible timing. I will say testosterone has had a huge impact for me personally, so I will be touching on it more during this series.
How early it starts — and why it gets missed
They say perimenopause usually starts in the mid-40s, roughly eight to ten years before menopause. But the range is wider than most of us are told: it can start as early as your mid-30s or as late as your mid-50s.³ For me it started at 35. Emotionally, I felt off, my skin started changing on my hands, and I noticed my baseline body temperature was slightly higher than normal (which was weird since I’ve been cold my whole life). I think most women don’t even know when they’re starting because they don’t understand the symptoms so it gets attributed to something else. I know for me I had no idea what was happening and I guarantee menopause was not at the top of the list of possibilities (after all that was something that happened much later in life).
Four primary reasons this stage goes unrecognized:
The testing doesn’t really work. This is the one that makes women feel crazy. Because your hormones swing day to day, a single blood draw is a snapshot of one moment in time, in a system that won’t hold still. FSH (Follicular Stimulating Hormone) testing can be especially misleading, since those numbers rise and fall erratically the whole way through. Diagnosis actually rests on your symptoms, your age, and your cycle history — not a lab result.³ I cannot overstate this. Diagnosis is based on how you feel — not on lab results! You can feel genuinely unwell and still get handed a normal panel. Seeing someone that understands women’s hormones cannot be emphasized enough. I will give my recommendations in my next post.
Your periods can stay regular at first. Cycle changes are the classic sign, but in the early years cycles often look fine while everything else is already happening. If you wait for irregular periods before you consider perimenopause, you can lose years of understanding what is happening to your body, mind, and mood.
A lot of doctors were never taught it. Don’t assume that just because they are a doctor or even an gynecologist that they are going to understand this. There are plenty of women who are experiencing it themselves and are doctors and they don’t connect the two. There was a 2023 survey of 99 OB/GYN residency program directors that found that only 31.3% of programs included any menopause curriculum. Every program that reported lectures gave five or fewer a year, and 71% gave two or fewer. Almost 84% of the directors themselves said they needed more resources.⁴ These are the programs training the doctors we go to. It makes sense to find someone who specializes in women’s hormones.
The symptoms look like everything else. Fatigue, mood changes, weight changes, joint pain, brain fog — that list belongs to a dozen conditions. Thyroid disease, anemia, vitamin deficiencies, and sleep disorders all overlap with it. Which cuts both ways: perimenopause gets missed, and so does whatever else might actually be going on. That deserves its own article because you definitely want to fix what can be fixed and not just chalk it up to perimenopause if that’s not what’s happening. But this point matters because so many doctors will attribute it to depression, anxiety, stress, and a host of other things that will never actually address the fluctuating hormones – so your symptoms never get better – you just end up wasting a lot of money and feeling like you’re going crazy.
I’m not a doctor and this isn’t medical advice. Everything here could overlaps with thyroid problems, anemia, and other treatable things — please get those ruled out with someone who can order the labs.
References
- Prior JC, Hitchcock CL. The endocrinology of perimenopause: need for a paradigm shift. Frontiers in Bioscience (Scholar Edition). 2011;3(2):474–486.
- Harlow SD, Gass M, Hall JE, et al. Executive summary of the Stages of Reproductive Aging Workshop +10. Fertility and Sterility. 2012;97(4):843–851.
- Cleveland Clinic. Perimenopause: Age, Stages, Signs, Symptoms & Treatment.
- Allen JT, Laks S, Zahler-Miller C, et al. Needs assessment of menopause education in United States obstetrics and gynecology residency training programs. Menopause. 2023;30(10):1002–1005.
- Testosterone and pre-androgens by age and menopausal stage at midlife: findings from a cross-sectional study. eBioMedicine. 2025.
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