Cortisol - fight or flight

Cortisol and cortisone, you hear both terms repeatedly in different contexts. Whether as an ointment, as a stress hormone, or as a medication. What are the differences between the molecules and what does the hormone actually do?

What is cortisol?

Cortisol is a hormone from the group of glucocorticosteroids, which is produced in the outer layer (cortex) of our adrenal glands. The adrenal gland sits as an independent organ on the kidney, is important for our water and salt balance, and its cortex is an important production site for many hormones.

But let's stick with cortisol: After it is produced in the adrenal cortex (AC), it enters our bloodstream and can act from there at practically all places in our body.

It binds to a receptor that is found in almost all tissue structures and thereby triggers many different reactions. For example, in stressful situations, it influences metabolism, blood pressure, heart rate, and the immune system.

The adrenal glands sit like small triangular caps on the kidneys. The outer part of the adrenal gland, also called the cortex, is the production site of cortisol.

How does cortisol work in the body?

Cortisol is a versatile hormone that is involved in many processes in the body. Especially in stressful situations, it plays a central role by providing energy and regulating important bodily functions.But how exactly does cortisol work?

Cortisol as a stress hormone

Our body is controlled by two antagonists in the nervous system: sympathetic and parasympathetic. While the parasympathetic is active during rest phases (“rest and digest”), the sympathetic takes over in stressful or challenging moments (“fight or flight”).

When a stressful situation arises – whether due to time pressure, physical strain, or a dangerous situation – the sympathetic activates the so-called stress hormone system. In addition to the well-known catecholamines adrenaline and noradrenaline, cortisol is also released.

Main task: Generate energy

One of the main tasks of cortisol is the provision of energy so that the body can quickly respond to a stressor. This occurs through the following mechanisms:

Increase in blood sugar level → So that the brain and muscles receive enough energy
Promotion of fat and muscle breakdown → Energy reserves are mobilized
Faster oxygen supply → Blood pressure and heart rate increase

These processes help to be more efficient in the short term – whether in sports, in exam situations, or during sudden stress.

Regulation of the Immune System

Cortisol is not only a stress hormone but also an important regulator of the immune system. It influences how our body responds to infections, inflammations and healing processes. But why does stress weaken our immune system – and why is cortisol specifically used as a medication?

Cortisol suppresses immune responses

In acute stress situations, cortisol ensures that the body reserves its energy for survival – not for healing processes.This means:

Wounds heal more slowly → The body prioritizes fight or flight
Allergic reactions are suppressed → The immune response is downregulated
Inflammation decreases → The body conserves energy for other processes

In the short term, this reaction can be sensible, but in the long run, it weakens the immune system. Those who are under chronic stress are often more susceptible to infections, as the body can no longer effectively combat pathogens.

Cortisone as a medication – why it works

Cortisone, the inactive precursor of cortisol, is often used as a medication for inflammation and autoimmune diseases.As soon as it enters the body, it is converted into the active Cortisol.

Applications of cortisone:

Treatment of allergies (e.g., hay fever, asthma)
Relief of inflammation (e.g., joint pain, skin issues)
Use in autoimmune diseases (e.g., rheumatism, multiple sclerosis)

However, long-term cortisone therapy can have side effects, as it affects the body's natural cortisol balance. Therefore, it is usually prescribed only for limited periods or in low doses.

Are cortisol levels too high? Why this is problematic

While a short-term increase in cortisol is completely normal, a persistently elevated cortisol level can have negative consequences. The body then remains in a kind of chronic stress mode, which is burdensome in the long run.

Especially insidious: One often does not directly feel chronically elevated cortisol. Many people get used to ongoing stress but do not realize that their body is constantly running at full speed.

Causes of elevated cortisol levels

A persistently elevated cortisol level can be triggered by various factors – both external stressors and internal physiological processes.

Physical or emotional stress

Whether it's intense workouts, lack of sleep, or emotional burdens – any type of stress activates cortisol production. Chronic stress prevents the body from adequately breaking down cortisol.

Professional or personal pressure

Constant time pressure, high responsibility, or conflicts in personal life can keep cortisol levels consistently high. Without sufficient recovery phases, the body remains in stress mode.

Excessive alcohol consumption

Alcohol affects hormone regulation and can increase cortisol release. At the same time, it burdens the liver, further deteriorating the body's ability to cope with stress.

Too much caffeine

Caffeine stimulates the sympathetic nervous system and signals the body to release cortisol – especially when consumed regularly and in high amounts.

Depression &and psychological stress

Studies show that people with depression often have elevated cortisol levels. Chronic emotional stress can permanently disrupt hormonal balance and lead to overproduction.

Hypoglycemia (low blood sugar)

A low blood sugar level signals a potential threat to the body. To provide energy, cortisol is released as it stimulates glucose production in the liver.

Hormonal Changes

Pregnancy, menopause, or diseases that affect hormone balance can also lead to an imbalance in cortisol production.

Long-term use of corticosteroid medications

Medications containing cortisone (e.g., for the treatment of inflammation or allergies) can affect the body's natural cortisol balance and inhibit or increase its own production.

Hyperfunction of the adrenal cortex (Cushing's syndrome)

In rare cases, a pathological overproduction of cortisol can be caused by a malfunction of the adrenal cortex or the pituitary gland. This leads to a persistently elevated cortisol level with serious health consequences.

The consequences

Sleep problems
Rising blood sugar levels
High blood pressure
Overweight
Coronary heart disease
Cushing's syndrome
Loss of libido
Weakness
Stomach problems
Weight gain

In contrast, a chronic Cortisol deficiency causes other symptoms:

low blood pressure
Weight loss
Mood swings
Weakness attacks

Cortisol throughout the day

Cortisol follows a natural rhythm that is aligned with the body's internal clock.Its concentration in the blood fluctuates throughout the day and is strongly influenced by sleep, stress, and daily routines.

In the morning: Highest cortisol level for the perfect start

Between 6 and 9 a.m., cortisol reaches its peak. This is because the body prepares for waking up:

Energy is mobilized to actively start the day
Blood sugar rises to fuel the brain
Alertness and attention increase

Tip: Getting plenty of daylight in the morning can help stabilize the natural cortisol rhythm. Here’s the ideal morning routine.

During the day: fluctuations depending on activity

Throughout the day, cortisol levels gradually decrease. However, depending on how stressful daily life is, short-term cortisol spikes can occur – for example, during meetings, intense workouts, or time pressure.

Those who experience a lot of stress during the day repeatedly produce cortisol – this can lead to an imbalanced hormone level in the long term.

High stress in daily life and at work reduces the immune system's ability to respond to threats.

In the evening: cortisol drops to its lowest point

By midnight, cortisol reaches its lowest value. Now, regeneration is in the foreground: Cells are being repaired The body prepares for sleep Relaxation and recovery begin Tip: Blue light from screens and late caffeine can artificially keep cortisol levels high – it's better to avoid digital devices two hours before going to bed. Here is the ideal sleep routine. Why a stable cortisol rhythm is important A healthy cortisol course is crucial for performance, well-being, and sleep quality.People with chronic stress often experience unnatural fluctuations:

Consistently high cortisol levels → Can lead to sleep disturbances, weight gain, and burnout
Too low cortisol levels → Can cause fatigue, lack of drive, and concentration problems

Measuring cortisol levels: How meaningful is it?

If you suspect that your cortisol levels are too high or too low, you can have them tested medically. However, a single measurement is not sufficient, as cortisol fluctuates significantly throughout the day. To obtain a meaningful result, the daily course of cortisol must be recorded and a so-called cortisol daily profile created.

How can cortisol be measured?

There are various methods to determine cortisol levels:

Blood test:

Measures total cortisol in the blood (bound &and free)
Meaningful for a moment, but not for the daily course

Urine or saliva test:

Captures the free, biologically active cortisol
Multiple measurements throughout the day possible to analyze the rhythm
Especially helpful in case of suspicion of imbalances throughout the day

Important: The saliva measurement is practical, but there are no standardized reference values, which can make interpretation difficult.

When is a cortisol measurement useful?

A test can be helpful if symptoms such as persistent exhaustion, sleep disturbances, unexplained weight gain, or concentration problems are present. Also, if there is suspicion of adrenal insufficiency or excessive stress, regular measurement can provide insights.

Anyone who wants to test their cortisol levels should measure it throughout the day in most cases to consider the natural rhythm. Individual values are not very informative.

Moleqlar Cortisol can be measured in blood serum (shown here), urine, and saliva. The normal values vary depending on the time of day.

Lowering cortisol levels: Practical tips

A persistently elevated cortisol level can negatively affect your health – from sleep disturbances to a weakened immune system. The good news: There are numerous simple methods that can positively influence your cortisol level.

Actively reduce stress

Chronic stress is one of the biggest drivers of cortisol.To get your body out of the “fight or flight” mode, targeted relaxation techniques can help:

Breathing exercises &and mindfulness training – have been shown to lower cortisol levels
Walks in nature – naturally reduce stress hormones
Power naps &and rest breaks – help the body to regenerate

Tip: Regular mindful breaks in everyday life can effectively regulate cortisol.

Healthy sleep for a stable cortisol level

Since cortisol follows a circadian rhythm, sleep is essential for its regulation. Those who sleep too little or irregularly risk persistently high cortisol levels.

Maintain regular sleep times – for a stable internal clock
Avoid blue light – keep at least one hour away from your phone and computer in the evening before going to bed to avoid disrupting natural cortisol reduction
Sleep duration of 7–9 hours – promotes recovery and lowers cortisol

Tip: A dark, cool bedroom can improve sleep quality and thus cortisol balance.

Nutrition & manage caffeine wisely

Your diet also influences your cortisol levels.

This can lower cortisol:

Magnesium-rich foods (e.g. nuts, leafy greens, bananas)
Omega-3 fatty acids (e.g. salmon, chia seeds)
Adaptogenic plants (e.g. Ashwagandha, Rhodiola)

This can increase cortisol:

Too much caffeine – stimulates the stress hormone system
Alcohol &and highly processed foods – additionally burden the body
Long periods of hunger – can cause cortisol levels to rise

Tip: If you are sensitive to caffeine, try to avoid it in the afternoon or evening to keep your cortisol levels from rising unnecessarily.

Movement – but in the right dose

Exercise can help lower cortisol – but only if it is done in moderation.

Moderate training (e.g., yoga, swimming, walking) → sustainably lowers cortisol
Intensive training (e.g., excessive cardio, HIIT) without recovery → can significantly increase cortisol in the short term

Tip: Ensure adequate recovery after training to keep cortisol levels stable.

Sources

Literature

https://www.spektrum.de/lexikon/biologie/cortisol/15438
https://www.zentrum-der-gesundheit.de/krankheiten/psychische-erkrankungen/stress/cortisol
Doccheck Flexicon
Springer Spektrum: Purves Biology (9th edition)
Fogelman, Nia, and Turhan Canli. “Early life stress and cortisol: A meta-analysis.” Hormones and behavior 98 (2018): 63-76.
El-Farhan, Nadia et al. “Measuring cortisol in serum, urine and saliva – are our assays good enough?.” Annals of clinical biochemistry 54.3 (2017): 308-322.

Graphics

Images acquired under license from Canva.

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