Cortisol: The stress hormone

Cortisol is synthesised by the adrenal glands, located just above the kidneys. Belonging to the glucocorticoid category, it plays a central role in regulating several vital functions such as metabolism, immune response and stress management. Cortisol production is finely regulated by the hypothalamic-pituitary-adrenal (HPA) axis, a complex system that is activated specifically in response to stressful situations.

The functioning of this axis begins in the hypothalamus, a small region of the brain that responds to stress signals by secreting the hormone CRH (corticotropin-releasing hormone). This hormone then travels to the pituitary gland, located at the base of the brain, which responds by releasing ACTH (adrenocorticotropic hormone) into the bloodstream.

Once in the bloodstream, ACTH acts on the adrenal glands, stimulating them to release cortisol. This cascade mechanism ensures a rapid response by the body to imminent challenges. The main role of cortisol is to mobilise the energy needed to face these challenges, in particular by increasing blood glucose levels, which supports vital functions and prepares the body to respond effectively. Cortisol is therefore essential in helping the body manage stress in an adaptive way, ensuring that energy resources are available for a rapid and effective response.

Cortisol is essential for the proper functioning of our bodies, and not just in the context of stress. Its main roles include:

Mobilisation of energy: In response to a threat, cortisol helps release glucose stored in the liver, thereby increasing blood sugar levels and providing energy to the muscles.

Reducing inflammation: Cortisol has anti-inflammatory properties. By reducing inflammation, it protects the body from an excessive immune response that could damage tissue.

Maintaining blood pressure: Cortisol plays a role in regulating blood pressure by controlling the balance of electrolytes (particularly sodium and potassium) in the blood.

Regulation of metabolism: It promotes the breakdown of fats, proteins and carbohydrates, helping to maintain stable energy levels throughout the day.

Influences mood: Studies have shown that cortisol plays a role in regulating mood. It is involved in managing emotions and can influence conditions such as depression and anxiety when it is in excess or deficient.

Preparation for the "fight or flight" response: This is undoubtedly the best-known function of cortisol. When faced with a dangerous situation, it prepares the body to react by increasing the heart rate, improving alertness, and optimising energy availability.

Although cortisol is essential for maintaining the balance of many bodily functions, excess cortisol can have significant adverse effects. This is often the case in situations of chronic stress, where the body continues to produce high levels of cortisol over long periods of time. Here are the main effects of excess cortisol:

• Hyperglycemia: Cortisol stimulates the production of glucose from proteins and fats, which can lead to high blood sugar levels in the long term. This increases the risk of developing type 2 diabetes.

• Immune dysfunction: Cortisol suppresses white blood cell activity and can weaken the immune response. People with high cortisol levels are more likely to get sick because their immune systems are less effective.

• Weight gain: Cortisol stimulates appetite, particularly for high-calorie foods such as fats and sugars. It also promotes fat storage, particularly in the abdomen, which increases the risk of abdominal obesity, which is associated with several metabolic diseases.

• Sleep disorders: High cortisol levels, especially at the end of the day, can disrupt circadian rhythms and lead to sleep disorders such as insomnia. Cortisol interferes with the production of melatonin, the hormone responsible for sleep.

• Decreased bone density: Excess cortisol inhibits calcium absorption and decreases bone formation, which can lead to osteoporosis in the long term.

• Cognitive problems: High cortisol levels can impair certain brain functions, including memory and concentration. Chronic stress is often associated with an increased risk of cognitive impairment and mental decline, especially in older adults.

Cortisol levels fluctuate naturally throughout the day, peaking in the morning before gradually decreasing to their lowest point in the evening. However, this cycle can be disrupted by several factors that cause an abnormal increase in cortisol.

Emotional or psychological stress: is one of the main drivers of this prolonged elevation of cortisol. In situations of intense and continuous stress, such as relationship conflicts or work pressures, the hypothalamic-pituitary-adrenal axis, which regulates cortisol production, is overstimulated, leading to a sustained increase in the secretion of this hormone.

Physical activity: although generally beneficial, can also influence cortisol levels if it is excessive or practiced without sufficient recovery. Training that is too intense or too frequent, without adequate breaks, can stimulate excessive cortisol production, thus upsetting the body's hormonal balance.

Sleep disturbances: such as sleep deprivation or irregular sleep schedules, also exacerbate this phenomenon. Lack of sleep or poor-quality sleep can cause inappropriate cortisol release during the night, disrupting the quality of rest and the body's homeostasis.

Excessive caffeine consumption: also affects cortisol levels. This substance stimulates the release of cortisol into the bloodstream, so excessive consumption of coffee or other caffeinated beverages can cause a temporary rise in the level of this hormone.

Diet: plays a key role in regulating cortisol. An unbalanced diet, rich in simple sugars and saturated fats, can alter cortisol levels, as can a deficiency in essential micronutrients such as B vitamins, magnesium, and zinc. In addition, certain diseases, such as Cushing's syndrome, which is characterised by excessive cortisol production by the adrenal glands, or other hormonal disorders, can cause abnormally high levels of this hormone. These conditions require medical intervention to correct the underlying causes and alleviate the symptoms associated with excess cortisol.

Indicative signs

Detecting excess cortisol can be complex, as the manifestations of this hormonal imbalance are often diverse and nonspecific. The most commonly observed symptom is chronic fatigue. This feeling of exhaustion can also coexist with significant weight gain, especially around the waist, which can affect body composition and fat distribution.

These physical changes are often accompanied by cognitive difficulties such as memory or concentration problems, hindering the ability to function on a daily basis. Emotionally, it is not uncommon to experience depression or anxiety, exacerbated by hormonal imbalance. At the same time, excess cortisol can weaken the immune system, making the body more vulnerable to frequent infections, another potential warning sign.

More specifically

A blood test is one of the most common ways to assess cortisol levels. This test is usually performed in the morning, when the hormone naturally peaks, in order to accurately measure cortisol levels, i.e., the amount of cortisol in the plasma. In addition, a saliva test may be prescribed to examine cortisol variations over a 24-hour period, providing an overview of the circadian rhythm of this hormone.

Finally, a urine test is also used to measure the amount of free cortisol excreted in the urine over a full day. This test reflects the amount of unbound cortisol in the body, providing an accurate picture of active hormone production. These different testing methods provide a reliable diagnosis, which is essential for guiding the management and treatment of excess cortisol.

Having too much cortisol is problematic because it interferes with many essential bodily processes. For example, high levels can impair the normal functioning of the cardiovascular system, leading to high blood pressure due to water and salt retention, which increases the risk of heart disease. Metabolically, excess cortisol stimulates gluconeogenesis, the process by which glucose is synthesised from proteins and lipids, potentially leading to chronic hyperglycemia and increasing the risk of insulin resistance and type 2 diabetes. Finally, prolonged high levels of cortisol can have a negative impact on mental health, exacerbating certain conditions such as depression and anxiety through deleterious effects on neurotransmission and brain neuroplasticity.

Regulating cortisol levels naturally is possible through several strategies and a healthy lifestyle. Here is a list of natural solutions for reducing cortisol:

1. Practice meditation: Meditation, particularly mindfulness meditation, has been shown to be effective in lowering cortisol levels in people under stress.

2. Improve sleep quality: Getting enough sleep (7-9 hours per night) and maintaining a regular sleep routine can help restore normal cortisol levels.

3. Engage in moderate exercise: Moderate physical activity, such as walking, yoga, or swimming, can help reduce stress and regulate cortisol.

4. Eat a balanced diet: Reducing your intake of refined sugars and processed foods, while increasing your intake of vegetables, fruits, and healthy fats, can help regulate cortisol.

5. Spend time in nature: Studies have shown that spending time in natural environments reduces stress and lowers cortisol levels.

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If you experience symptoms that could indicate a cortisol imbalance, such as unexplained weight gain, persistent fatigue, sleep disturbances, drops in blood pressure, or headaches, it is strongly recommended that you consult a healthcare professional.

These signs may reflect abnormal cortisol production, whether excessive or insufficient. This situation requires medical advice to identify the specific cause and determine the appropriate treatment.

Do not take any treatment or dietary supplements intended to alter cortisol levels without medical advice. Doing so could aggravate the imbalance or mask the symptoms of an underlying health problem.

If you experience any of the symptoms described above, try adopting some good habits: sleep longer, meditate, eat a more varied and balanced diet... Your body is sending you signals, listen to them! If the symptoms do not go away within a few days or weeks, consult your doctor.

Stéphanie is a pharmacist (since 2010) and holds a PhD in molecular biology (since 2012). Passionate about writing, she has produced medical content for nearly 15 years. Her goal is to make information accessible and easy to understand, without ever sacrificing scientific accuracy.