Cortisol Pt 2: What Happens When the Body is Under Pressure
Cortisol does much more than help the body respond to stress. In this second part of our deep dive, we continue exploring how this essential hormone influences your health from the inside out.
Cortisol often gets a bad rap as the “stress hormone,” but it's actually a vital player in keeping our bodies balanced and resilient. Produced by the adrenal glands, cortisol helps us respond to challenges, regulate energy, and maintain stability during times of stress.
The HPA Axis: Orchestrating the Stress Response
When we encounter stress, be it physical danger, illness, or psychological strain, our body activates the hypothalamic-pituitary-adrenal (HPA) axis. This system involves a cascade: the hypothalamus releases corticotropin-releasing hormone (CRH), prompting the pituitary gland to secrete adrenocorticotropic hormone (ACTH), which then signals the adrenal glands to produce cortisol.
Once cortisol is released into the bloodstream, it helps the body rise to the occasion. It boosts blood sugar levels to provide quick energy for your brain and muscles, and it helps maintain blood pressure to keep blood flowing to vital organs. At the same time, cortisol shifts the body’s priorities. It temporarily puts long-term processes like growth, reproduction, and certain parts of the immune system on hold. The body focuses all its resources on getting through the challenge in front of it.
This built-in shift is part of what scientists call allostasis. Instead of aiming for perfect balance, the body finds a new temporary set point that allows it to adapt to stress and keep functioning. In the short term, this response is not just helpful, it can be life-saving.
Cortisol works alongside adrenaline to help you act fast and store the memory of what happened. These two hormones are part of the reason emotionally intense events become etched in your memory. Known as “flashbulb memories,” these lasting impressions help us learn from past danger and avoid it in the future.
But this system was designed for short bursts of stress, not constant pressure. When stress becomes chronic, cortisol can stay elevated for too long, which creates problems over time. This state is often referred to as high allostatic load, meaning the body is under ongoing strain from trying to adjust again and again.
One of cortisol’s most sensitive targets is the hippocampus, a key region in the brain that supports memory and learning. Long-term exposure to high cortisol levels can damage or shrink cells in the hippocampus (1), which may explain why chronic stress often leads to brain fog, forgetfulness, or trouble concentrating.
Cortisol has also been linked to changes in mood. In some individuals, persistently high levels of cortisol are associated with anxiety, low mood, or symptoms of depression (2). While cortisol is critical when we’re facing immediate stress, it becomes harmful when it never gets a chance to reset. That’s why stress recovery is just as important as stress response. Supporting your body’s natural rhythms and managing stress can help keep cortisol in a healthy range, protecting both your brain and your overall well-being.
Cortisol’s role in managing stress is only part of the story. This hormone also plays a key part in how your body manages energy day to day. Whether you're waking up in the morning, skipping a meal, or navigating a high-pressure moment, cortisol helps ensure your cells have the fuel they need to keep going. Understanding these metabolic effects gives us a fuller picture of how cortisol supports both immediate survival and long-term balance.
Metabolic Effects: Fueling the Body
Cortisol belongs to a group of hormones called glucocorticoids, which hints at one of its main jobs: managing glucose, or blood sugar. One of cortisol’s core responsibilities is to keep your body’s energy supply steady, especially during times when food is scarce or when demands are high. It does this by coordinating a few key metabolic processes behind the scenes.
Raising Blood Sugar When It’s Needed Most
When cortisol levels rise, the liver gets the signal to start producing new glucose. Cortisol also helps release stored glucose by breaking down glycogen, which is the storage form of sugar, in the liver and muscles. These actions raise blood sugar levels when the body needs quick fuel, whether you're fasting, under stress, or just waking up in the morning. This helps prevent your blood sugar from dropping too low and keeps your brain and muscles energized.
Breaking Down Stored Resources for Energy
To support that glucose production, cortisol encourages the breakdown of stored nutrients. In muscle tissue, it promotes the breakdown of proteins into amino acids. In fat tissue, it stimulates the release of fatty acids that the body can also use for energy. This ability to break down and repurpose stored resources makes cortisol a catabolic hormone, essentially allowing the body to tap into its savings to meet energy demands in a way that once supported survival long before regular meals were part of daily life.
Prioritizing Fuel for the Brain
Cortisol also helps prioritize energy delivery to the brain, ensuring it has access to the fuel it needs. It does this by making muscle and fat cells slightly less responsive to insulin, which reduces how much glucose they absorb (3). This keeps more glucose circulating in the bloodstream, readily available for your brain and other vital organs. In short bursts, this is helpful. But when cortisol remains high for long periods, this same mechanism can lead to elevated blood sugar and increase the risk of insulin resistance.
All these effects work together to keep energy flowing to the right places at the right time. For example, cortisol naturally rises in the early morning hours, helping to increase your blood sugar and wake up your brain. People with low cortisol levels, such as in Addison’s disease, often feel especially fatigued in the morning and may struggle with low blood sugar, which underscores how essential this hormone is for metabolic balance.
When Cortisol Is Constantly High
While cortisol is incredibly useful in the short term, problems can arise when it stays elevated for too long. Ongoing breakdown of muscle can lead to weakness over time, and the combination of high blood sugar and insulin resistance may contribute to weight gain or even a form of diabetes known as steroid-induced diabetes. People with abnormally high cortisol levels, such as those with Cushing’s syndrome or under chronic stress, often experience increased abdominal fat, elevated glucose, and signs of metabolic syndrome.
This reflects an important biological trade-off. Cortisol is built to help you survive short-term stressors by mobilizing energy quickly. But when that stress becomes a daily pattern, the same survival tools can become harmful. That’s why healthy cortisol rhythms, rising in the morning and gently falling throughout the day, are so important for long-term metabolic health.
Dr. Jonathan Moustakis
Co-founder and CTO of Lume Health
References
Kim EJ, Pellman B, Kim JJ. Stress effects on the hippocampus: a critical review. Learn Mem. 2015;22(9):411–416. https://doi.org/10.1101/lm.037291.114
Dziurkowska E, Wesolowski M. Cortisol as a biomarker of mental disorder severity. J Clin Med. 2021;10(21):5204. https://doi.org/10.3390/jcm10215204
Janssen JAMJL. New insights into the role of insulin and HPA axis in metabolic syndrome. Int J Mol Sci. 2022;23(15):8178. https://doi.org/10.3390/ijms23158178
