How Fall Throws Your Hormones Off Balance

Summer ends, and suddenly the calendar fills up. The kids are back in the swing of school, sports, and clubs. Then come shorter days, the holidays, and more stress, and you feel wired and tired at the same time.

You’ve probably heard it before: “It’s just stress.” Let me tell you, it’s more than that. It’s a physiological response.

I saw this firsthand as a critical care nurse. We place critically ill patients in small rooms with no natural light, interrupt their sleep around the clock, and then expect them to heal. Their bodies are already in a literal fight for their lives, and we make it harder. The brain gets confused, and the body loses its rhythm. Then, when we get them into natural light, restore a more normal day-and-night routine, and stop interrupting their sleep so often, the body responds.

Your everyday life isn’t an ICU, and the shifts are nowhere near as drastic. But changes in light, disrupted sleep, and ongoing stress are small shifts that add up, and they have a big impact on how your body responds.

So let’s walk through what’s happening, what your symptoms are signaling, and what to do with that information.

Fall Is a Biological Transition, Not Just a Calendar Change

Fall brings holiday decor, comforting soups, and pumpkin spice everything. It also brings less daylight and cooler temperatures, and that matters more than most of us realize.

Your brain uses light as its main signal for timing hormone release.1,2 When you wake up and sunlight reaches your eyes, it helps set off the chain of signals that tell your body to get going, including a rise in cortisol that gives you energy for the day. Your circadian rhythm, the body’s master clock, coordinates cortisol, melatonin, and energy across the 24-hour day.1,2

With later sunrises and earlier sunsets, those signals shift. Your cortisol awakening response, the natural surge of cortisol in the first hour after waking, is sensitive to light.1 Where you live changes the picture, too. Seasonal symptoms are more common at higher latitudes, so your rhythms in Alaska will look different from your rhythms in Arizona.1,2 But wherever you are, your body is adapting to a new season, and when that adjustment lags, it can feel like something is wrong when it’s really a mismatch between your body’s clock and your environment.

And if your baseline was already off before fall arrived, this adjustment can hit harder, which is why your energy may be the first thing to show it.

Cortisol: The Hormone That Takes the Hit First

Cortisol is a key player in your circadian rhythm. In a healthy pattern, it starts rising a couple of hours before you wake, surges in the first hour after you open your eyes, and then gradually declines through the day, reaching its lowest point late at night.1,3

Light plays a big role in that morning surge.1 When sunrise shifts from 5 a.m. to 7 a.m., you may be getting up in the dark, and that can blunt the surge. Add stress and a busier schedule, and the curve can flatten or even flip. Flattened cortisol patterns are well documented in people under chronic stress, and they’re associated with poorer health outcomes.3,4

What does that feel like? Symptoms many women write off as laziness: you wake up tired, you crash in the afternoon, or you get a second wind right before bed. That wired and tired feeling can be soul crushing, especially when you’re wide awake at 3 a.m. The later sunrise and the stress of the season have created cortisol chaos, and your body is showing you the toll.

And it’s not just the later sunrise. The earlier sunset changes the timing of cortisol’s counterpart, melatonin.2

Melatonin, Sleep, and the Domino Effect

If cortisol is your wake-up and energy hormone, melatonin is its opposite: your wind-down signal. It’s the other half of your circadian rhythm. When the sun sets and your body senses darkness, melatonin rises to tell your body it’s time to sleep.

As fall arrives and darkness comes earlier, that signal can start earlier too, as long as artificial light doesn’t override it.2 Evening light, including the light from phones, tablets, and other screens, can delay and reduce melatonin release. In one study, people who read on a light-emitting device before bed took longer to fall asleep, made less melatonin, and felt less alert the next morning than when they read a printed book.5 That’s why dimming the lights and putting screens away in the evening matters.

When melatonin is delayed or reduced, your brain doesn’t get a clear “time for bed” message, and your sleep rhythm can slip. Your cortisol rhythm tends to follow your sleep-wake pattern,6 so when sleep is disrupted, cortisol timing is thrown off too. Appetite and cravings tend to increase when you’re short on sleep,7 and blood sugar becomes harder to regulate.8 Mood takes a hit as well. Sleep loss consistently lowers positive mood and raises anxiety.9

That’s why the first domino to fall is so often sleep disruption.

Blood Sugar, Cravings, and Why You Want Comfort Food

Cortisol is built to prepare you for danger. When your body perceives a threat, it signals your liver to release glucose into your bloodstream,10 so you have fuel for the proverbial lion chase. That’s brilliant when the threat is short-lived. But when stress is constant (school schedules, deadlines, holiday planning, shorter days), the system never fully switches off. Your blood sugar stays pushed up, and your pancreas keeps releasing insulin to manage it. Over time, chronically elevated cortisol also makes your cells less responsive to insulin,11 which means bigger swings: spikes, then crashes that leave you tired, shaky, and hungry.

Stress also changes what you want to eat. Research shows that stress and cortisol increase appetite and a preference for calorie-dense foods high in sugar and fat, and eating them can temporarily calm the body’s stress response.12 So the pull toward comfort carbs isn’t random. It’s biology.

Sleep loss adds fuel to the fire. In one classic study, healthy young adults who slept only four hours a night for less than a week had reduced glucose tolerance and higher evening cortisol.8 Sleep-restricted people also tend to eat more.7 A rough night sets up a rough day: more stress hormones, shakier blood sugar, and stronger cravings. Answer those cravings with sugar, and the cycle starts again.

This is a signal that your body is struggling to keep up, not a willpower failure.

There may also be a gut connection. Your gut and your stress response communicate in both directions: chronic stress can change your gut microbiome and weaken the gut barrier, and gut bacteria can in turn influence the stress response.13 In animal studies, high-sugar diets have disrupted the gut barrier and promoted inflammation.14 Human research is still emerging, but it’s one more reason that steadying blood sugar and supporting your gut matter during a stressful season.

Thyroid, Sex Hormones, and Women Who Already Feel Stretched

Seasonal shifts add load to a system that may already be strained. Women in perimenopause, or whose thyroid or progesterone is already low, often feel it most. Perimenopause is a time of fluctuating estrogen and progesterone, both of which influence sleep, and sleep disturbance is very common during the transition.15,16 Thyroid function can shift with the seasons too. Studies show TSH tends to run higher in winter, although findings vary.17,18 In my practice, the women who are already depleted are the ones who notice fall first.

Now layer fall on top: sleep disruption, light changes, and a bigger carb and sugar load. Mornings are harder with the later sunrise, your cortisol rhythm is off, your blood sugar is swinging, and suddenly you’re reaching for the Halloween candy. Add the stress of the holidays and the kids, plus the nagging awareness that your diet and sleep schedule are off, and that awareness becomes its own stressor. The cycle continues.

When the strain doesn’t let up, your body compensates. Chronic stress and short sleep are both linked with weight gain, especially around the middle.7,12 Your mental clarity can suffer. And your body stays tilted toward fight or flight, in a kind of survival mode.

What Your Body Is Trying to Tell You: A Symptom Decoder

With seasonal changes, hormonal shifts, and holiday stress all happening at once, you may notice it as:

• Waking between 2 and 3 a.m.: A shifted sleep rhythm, higher evening cortisol, and the hormone changes of perimenopause can all fragment sleep.8,15,16

• Afternoon crashes: A flattened cortisol pattern combined with swinging blood sugar can make energy drop hard in the middle of the day.3,4,11

• Increased cravings: Stress and short sleep both increase appetite and pull you toward sugar and fat.7,12

• Mood dips or irritability: Sleep loss lowers positive mood and raises anxiety.9

• Brain fog: Poor sleep and fluctuating hormones can both cloud focus and mental clarity.5,15

• Cycle changes: Chronic stress can disrupt the signals that regulate ovulation,19 and stress-related cycle changes can look a lot like those of perimenopause.20

These aren’t flaws or failures. They’re information, your body telling you it needs support.

When to Look Deeper

Your body is meant to shift with the seasons, and some adjustment in fall is normal. The problem starts when your symptoms persist, get worse, or interfere with your daily life. You can’t seem to get off the couch, you struggle to keep up with your kids, or your sex life has taken a hit.

Then comes the frustrating part: your labs come back “normal,” and everything “looks fine.” Standard lab ranges are built from population averages, and they don’t always reflect what’s normal for you. Thyroid testing is a good example. Experts still debate where the upper limit of a normal TSH should sit, and a “normal” result doesn’t always mean you feel well or that your tissues are getting the thyroid hormone they need.21,22

As a registered nurse who is board certified in functional medicine, I take a different approach. I look for patterns across your symptoms, history, and labs. I look at optimal ranges rather than only whether a number falls inside the standard range, and I investigate the “why” behind what you’re feeling. That often tells a much fuller story. Being exhausted, overlooked, and told it’s “normal” is no longer acceptable.

And if you ever have sudden or severe symptoms, please don’t wait. Seek medical care right away.

Conclusion

Fall will keep changing your biology, just as every season does. Your symptoms are messages from your body, and you can respond to them with knowledge and power.

To start with some small, simple changes you can make in your daily life, download the Energy Boost Blueprint or schedule a time to talk with me. Link below.

You are worth investigating. Instead of letting the seasonal shift drag you down, let’s use it as a reset and an energy boost for change.

Root Cause Clarity Session

References

1.Latitude and endocrine consequences of human migration: seasonal affective disorder and the cortisol awakening response. Endocrine Abstracts, 2012; 28: S7.3. https://www.endocrine-abstracts.org/ea/0028/ea0028S7.3

2.Annual variation in daily light exposure and circadian change of melatonin and cortisol concentrations at a northern latitude with large seasonal differences in photoperiod length. Journal of Physiological Anthropology, 2016. https://doi.org/10.1186/s40101-016-0103-9

3.Diurnal cortisol slopes and mental and physical health outcomes: a systematic review and meta-analysis. Psychoneuroendocrinology, 2017. https://pmc.ncbi.nlm.nih.gov/articles/PMC5568897/

4.Young et al. Life stress and diurnal cortisol rhythm. Psychological Science, 2019. https://socialinteractionlab.psych.umn.edu/sites/socialinteractionlab.psych.umn.edu/files/files/media/young_et_al_ps_2019.pdf

5.Chang AM, et al. Evening use of light-emitting eReaders negatively affects sleep, circadian timing, and next-morning alertness. Proceedings of the National Academy of Sciences, 2015. https://pmc.ncbi.nlm.nih.gov/articles/PMC4313820

6.Tsuboi S, et al. Circadian periodicity of plasma cortisol levels in members of the Japanese Antarctic Research Expedition. Antarctic Record, 1976. https://doi.org/10.15094/00007882

7.Effects of experimental sleep restriction on weight gain, caloric intake, and meal timing in healthy adults. Sleep, 2013. https://pmc.ncbi.nlm.nih.gov/articles/PMC3669080

8.Spiegel K, Leproult R, Van Cauter E. Impact of sleep debt on metabolic and endocrine function. The Lancet, 1999.

9.Palmer CA, et al. Sleep loss and emotion: a systematic review and meta-analysis of over 50 years of experimental research. Psychological Bulletin, 2024. https://pubmed.ncbi.nlm.nih.gov/38127505/

10.Cortisol increases gluconeogenesis in humans: its role in the metabolic syndrome. Clinical Science (London), 2001. https://pubmed.ncbi.nlm.nih.gov/11724664/

11.Andrews RC, Walker BR. Glucocorticoids and insulin resistance: old hormones, new targets. Clinical Science, 1999.

12.Tomiyama AJ, Dallman MF, Epel ES. Comfort food is comforting to those most stressed: evidence of the chronic stress response network in high stress women. Psychoneuroendocrinology, 2011. https://pmc.ncbi.nlm.nih.gov/articles/PMC3425607/

13.The role of the adrenal-gut-brain axis on comorbid depressive disorder development in diabetes. Biomolecules, 2023. https://doi.org/10.3390/biom13101504

14.University of Alberta study of a short-term high-sugar diet, gut permeability, and colitis in mice. Scientific Reports, 2019 (news summary): https://www.ualberta.ca/en/folio/2019/11/sugar-binges-increase-risk-of-inflammatory-bowel-disease-study-suggests.html

15.Sleep disturbance and perimenopause: a narrative review. Journal of Clinical Medicine, 2025. https://pmc.ncbi.nlm.nih.gov/articles/PMC11901009

16.Haufe A, Baker FC, Leeners B. The role of ovarian hormones in the pathophysiology of perimenopausal sleep disturbances: a systematic review. Sleep Medicine Reviews, 2022.

17.Seasonal changes of thyroid function in women of reproductive age. Frontiers in Endocrinology, 2021. https://www.frontiersin.org/journals/endocrinology/articles/10.3389/fendo.2021.719225/full

18.Seasonal variation in thyroid function in over 7,000 healthy subjects. https://pmc.ncbi.nlm.nih.gov/articles/PMC9070835

19.Han Y, Lin X. The relationship between psychological stress and ovulatory disorders and its molecular mechanisms: a narrative review. Journal of Psychosomatic Obstetrics & Gynecology, 2024. https://doi.org/10.1080/0167482x.2024.2418110

20.Mini-review on stress, the kisspeptin system, and ovulatory dysfunction. Frontiers in Global Women’s Health, 2022. https://frontiersin.org/articles/10.3389/fgwh.2022.866104/full

21.Limitations of TSH reference ranges and individual thyroid set points (2012). https://pmc.ncbi.nlm.nih.gov/articles/PMC3529417

22.Review of the limitations of TSH as a marker of thyroid function and symptom resolution. https://pmc.ncbi.nlm.nih.gov/articles/PMC6778876