You held it together all day.
Productive at work. Present in meetings. Handling everything on your list.
Then 6pm hits — and the patience is gone. The irritability surfaces. The exhaustion is bone-deep. And the people closest to you get the worst version of you.
If this is a familiar pattern, it’s worth knowing: it’s not a character flaw. And it’s not just stress. It may be a sign that your cortisol awakening response and HPA axis — your body’s central stress response system — are dysregulated
What Is the HPA Axis and Why Does It Affect Your Energy?
The hypothalamic-pituitary-adrenal (HPA) axis is the system that governs your body’s cortisol output. When it’s functioning well, cortisol follows a predictable daily rhythm: it rises sharply in the morning, peaks mid-morning, and gradually tapers off through the afternoon and evening, reaching its lowest point around midnight.
This rhythm is what gives you energy in the morning, helps you sustain focus through the day, and allows you to wind down at night.
When the rhythm is disrupted — flattened, inverted, or blunted — the whole system is affected.
The Cortisol Awakening Response: What It Is and Why It Matters
One of the most clinically informative markers of HPA axis function is something called the cortisol awakening response (CAR) — the rapid spike in cortisol that occurs in the first 30–45 minutes after waking. In healthy individuals, this surge represents a 38–75% increase above baseline awakening levels. [1]
The CAR isn’t just a morning energy boost. Research suggests it serves two key functions: mobilizing metabolic, immune, and cognitive resources for the day ahead, and helping the body counterregulate adverse emotional experiences from the prior day. [1] It’s your body’s way of preparing for what’s coming.
When the CAR is blunted — meaning cortisol doesn’t rise adequately in that morning window — you start the day already behind. The resources your body needs to sustain energy, regulate mood, and manage stress aren’t fully mobilized. By the time evening arrives, there’s nothing left in reserve.
Signs of a Disrupted Cortisol Awakening Response
A blunted or dysregulated cortisol awakening response doesn’t always announce itself clearly. It often looks like this:
- Reaching for caffeine before your feet hit the floor
- Feeling foggy and slow in the morning, then finally hitting your stride mid-afternoon
- Being wired at night when you should be winding down
- The smallest things feeling like too much by evening
- Irritability that seems disproportionate to the situation
Research shows that people with chronic fatigue conditions have significantly blunted morning cortisol spikes compared to healthy controls. [2] And on a day-to-day level, a lower CAR in the morning predicts more physical symptoms later that same day — more pain, more exhaustion, more of everything. [3]
The rhythm also has long-term implications. A more robust CAR has been associated with lower cardiovascular mortality risk in prospective cohort studies with over a decade of follow-up. [4] The pattern matters — not just for how you feel today, but for your health over time.
Why This Hits Perimenopausal Women Especially Hard
For women in perimenopause, HPA axis dysregulation doesn’t happen in isolation. It intersects with the hormonal shifts already underway.
As the ovaries begin producing less estrogen and progesterone, the adrenal glands are asked to pick up some of that hormonal slack. The adrenals produce small amounts of estrogen precursors and progesterone — not enough to fully compensate, but enough to matter, especially in the transition years.
If those adrenals are already depleted from years of chronic stress output, there’s less reserve to draw from. The hormonal transition becomes harder. The symptoms — fatigue, mood instability, poor sleep, brain fog — become more pronounced. And because these symptoms overlap with so many other things, the HPA axis often goes unexamined.
This is one of the reasons I look at cortisol patterns in nearly every perimenopausal patient I work with. It’s not the only factor — but it’s a significant one that standard care rarely evaluates.
The Cortisol Awakening Response in Athletes and High Performers
For athletes and high performers, the training load adds another layer of complexity.
Your body doesn’t always distinguish between the stress of a hard workout and the stress of a difficult conversation — physiologically, it’s processing both as stressors that require cortisol output. When recovery isn’t keeping pace with output, the HPA axis can start to struggle.
Research on overtraining syndrome has found that a blunted morning cortisol response is one of its earliest signs — often appearing before performance fully breaks down. [5] A 2021 study specifically examining the CAR in overtrained athletes found it may be a useful biomarker for monitoring athlete readiness and detecting overtraining before it becomes a full syndrome.
That means the CAR isn’t just a stress marker. For athletes, it may be one of the first measurable signals that the body is asking for more recovery than it’s getting — before the performance data confirms it.
How We Test the Cortisol Awakening Response and HPA Axis
A single morning cortisol blood draw — the kind that might appear on a standard panel — misses most of this picture. The cortisol awakening response requires multiple salivary cortisol samples collected at specific intervals in the first hour after waking: typically at 0, 30, and 60 minutes post-awakening.
This is why I use salivary cortisol testing rather than relying on a single data point. It gives us the actual shape of the morning curve — whether the CAR is robust, blunted, or absent — and it tells us far more about how the HPA axis is functioning than a single number can.
Combined with a full diurnal cortisol pattern (samples throughout the day), we can see whether cortisol is too high, too low, inverted, or flat — and use that to guide a targeted treatment plan.
A Simple Way to Start Paying Attention
Before any testing, there’s a straightforward self-observation exercise worth doing:
Track your energy in three windows over the next few days — morning, mid-afternoon, and evening. Not how busy you are. How you actually feel.
If you’re consistently lowest in the morning, better by midday, and crashing or wired by evening — that’s a pattern. It’s not proof of HPA axis dysregulation, but it’s a signal worth investigating.
The Bottom Line
The 6pm crash isn’t inevitable. It’s not just aging, and it’s not just stress. For many of the women I work with, it’s a measurable, addressable pattern rooted in how the HPA axis is functioning — and how it’s intersecting with hormonal changes, training load, and years of high output.
If this resonates, the first step is a conversation.
A Discovery Call is a short conversation with our team to talk through what’s going on, what we’d look at, and whether Rise is the right fit for you. No pressure. Just a real conversation.
References:
- Stalder T. The Cortisol Awakening Response: Regulation and Functional Significance. Endocrine Reviews. 2025. https://pubmed.ncbi.nlm.nih.gov/39177247/
- Woo TW, et al. Neuroendocrine Signature of ME/CFS: Meta-Analytic Evidence for Bioactive Cortisol Deficit and Exaggerated Feedback Sensitivity. Molecular Psychiatry. 2026. https://www.nature.com/articles/s41380-026-03608-1
- Gartland N, O’Connor DB, Lawton R, Bristow M. Exploring Day-to-Day Dynamics of Daily Stressor Appraisals, Physical Symptoms and the Cortisol Awakening Response. Psychoneuroendocrinology. 2014. https://pubmed.ncbi.nlm.nih.gov/25217853/
- Karl S, Johar H, Ladwig KH, Peters A, Lederbogen F. Dysregulated Diurnal Cortisol Patterns Are Associated With Cardiovascular Mortality: Findings From the KORA-F3 Study. Psychoneuroendocrinology. 2022. https://pubmed.ncbi.nlm.nih.gov/35395560/
- Anderson T, et al. Effects of Overtraining Status on the Cortisol Awakening Response (EROS-CAR ). International Journal of Sports Performance and Physiology. 2021. https://journals.humankinetics.com/view/journals/ijspp/16/7/article-p965.xml
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