Is your cortisol too high? What your stress hormone really means

What is cortisol?

Cortisol is a vital hormone belonging to the group of glucocorticoids. It performs key functions in the human body and plays an important role in helping the body adapt to stress.

Cortisol is produced in the adrenal cortex. Among other things, it regulates the cardiovascular system and kidney function before it is eventually processed and broken down in the liver.

What functions does cortisol perform in the body?

Cortisol is often simplistically referred to as the ‘stress hormone’, but its functions are far more diverse. As a vital hormone, it influences almost every cell in the body to provide energy and maintain balance:

• The main role of cortisol is to raise blood sugar levels so that the body has immediate access to energy in stressful situations. It stimulates the liver to produce new glucose from proteins. It also promotes the release of fatty acids from adipose tissue. In muscles and bones, it promotes the breakdown of proteins into amino acids, which can then be used again for energy production.
• A second key function of cortisol relates to the immune system: cortisol has a strong immunosuppressive effect. This means it dampens excessive immune responses and inhibits inflammatory processes in the body. (The precursor to cortisol – cortisone – is frequently used as an anti-inflammatory or anti-allergic medication, for example in the treatment of bronchial asthma.)
• Cortisol also ensures that the circulatory system remains stable: it raises blood pressure by enhancing the effect of adrenaline and noradrenaline on the blood vessel walls (vasoconstriction). Furthermore, it regulates water and salt balance in conjunction with the kidneys.
• In acute stress situations, cortisol works hand in hand with adrenaline. Whilst adrenaline is responsible for the ‘immediate response’ (palpitations, sweating), cortisol ensures, over a longer period, that the body remains resilient and does not become exhausted prematurely.
• Other functions relate to bone metabolism: persistently high cortisol levels inhibit bone formation (risk of osteoporosis) and affect the central nervous system. It influences mood, concentration and memory. Too much cortisol can lead to sleep disturbances or inner restlessness in the long term.

Why does cortisol fluctuate throughout the day?

Cortisol follows a natural daily rhythm, known as the circadian rhythm. This ensures that hormone levels adapt to the change between day and night, as well as to the body’s energy requirements. In the morning, there is a sharp rise, which acts like a biological alarm clock, as it mobilises energy, raises blood pressure and wakes you up for the day.

During the day, levels gradually decrease as energy is expended, and at night they are at their lowest. This is necessary to allow the sleep hormone melatonin to take effect and for the body to regenerate.

Please note: Within this rhythm, there are factors that can alter the curve. For instance, light signals the brain to boost cortisol production, whilst darkness curbs it. Regardless of the time of day, acute stress leads to an immediate additional release. Cortisol also rises slightly after a meal to support the metabolism as it processes nutrients. Chronic stress can completely disrupt this rhythm.

What does ‘high cortisol’ mean?

An elevated cortisol level can generally have two causes: a short-term stress response or a persistently elevated hormone concentration. This is because in acute stress situations, a high level is normal and beneficial. It provides energy, suppresses pain and enhances focus. Once the situation is over, the level drops again. However, if the level remains persistently high (e.g. due to chronic stress or illness), there is too much of this hormone present, and that is harmful.

This can lead to a range of physical and psychological consequences:

• Weight gain: particularly around the abdomen (abdominal obesity).
• Muscle loss: Arms and legs become thinner.
• Skin changes: The skin becomes thin (‘parchment-like’), develops stretch marks or acne.
• High blood pressure: The cardiovascular system is under constant strain.
• Weakened immune system: You become more susceptible to infections.
• Sleep disturbances (you feel “tired but hyper”).
• Difficulty concentrating and anxiety.

What causes high levels?

Elevated cortisol levels can have various causes. Lifestyle factors often play a role, but medical causes may also be a factor.

• Lifestyle: Chronic stress caused by constant pressure at work, worries or emotional conflicts keeps levels permanently elevated. Too little or irregular sleep disrupts the circadian rhythm and also drives levels up. Extreme competitive sport without sufficient recovery periods also acts as a form of stress on the body. Finally, strict diets or fasting can also raise cortisol levels, as low blood sugar is a stress signal for the body, to which it responds by releasing cortisol to mobilise energy.
• Medical and external causes: Sometimes a physical illness is the cause of persistently elevated cortisol levels. These include endogenous Cushing’s syndrome: in this condition, excessive cortisol leads to central obesity, a moon-shaped face, a bull’s neck, diabetes and high blood pressure. This excess is often triggered by long-term use of cortisone-based medication or by tumours that stimulate the body’s own hormone production. Excessive alcohol consumption also activates the stress axis in the brain and can lead to what is known as ‘pseudo-Cushing’s syndrome’.

Short-term increases in cortisol

A short-term rise in cortisol is a vital response to acute stressors such as stress, physical exertion or anxiety, which boosts performance within seconds. Initially, cortisol floods the blood with glucose (sugar) so that the brain and muscles can work at full capacity. Concentration is sharpened, and unimportant stimuli are blocked out. The pain threshold rises – in an emergency situation, you continue to ‘function’ for the time being, even if you have injured yourself, and functions that would currently require too much energy are temporarily curtailed.

A short-term rise is healthy and intended. As soon as the stressful situation is over, levels return to normal. The problem only arises when the relaxation phase is missing. If cortisol levels remain persistently high, this helpful protective response becomes a burden on the body.

Chronically elevated cortisol and its consequences

A persistently elevated cortisol level (hypercortisolism) puts the body into a toxic state of chronic stress, and this can have fatal consequences:

• Physical changes: A characteristic redistribution of fat and tissue occurs. Typical signs include a rounder face and fat deposits on the neck and abdomen, whilst the arms and legs become thinner due to muscle wasting.
• Metabolic disorders: Cortisol acts as an antagonist to insulin. A persistent excess drives up blood sugar levels, which can lead to diabetes and high blood pressure.
• Bones and skin: The hormone inhibits the formation of new tissue. Bone density decreases (osteoporosis), the skin becomes thin and develops bluish streaks (striae), and wounds heal less effectively.
• Immune deficiency: Cortisol suppresses the immune system. This increases susceptibility to infection, whilst inflammatory responses in the body are partially dampened.
• Psychological and neurological effects: Chronically high levels lead to sleep disturbances (inability to wind down in the evening), anxiety, depressive moods and poor concentration.

Cortisol in women: menstrual cycle, the menopause and stress

Cortisol has a massive influence on the female hormonal system, as it is closely linked to the regulation of oestrogen and progesterone. It therefore also affects the menstrual cycle. Too much cortisol can, for example, cause irregular cycles or amenorrhoea (absence of periods), exacerbate PMS, or – during the menopause – lead to night-time hot flushes or the typical menopausal ‘belly’, and increase the risk of osteoporosis.

Cortisol and the menstrual cycle

The relationship between cortisol and the female menstrual cycle is a delicate balance. The body prioritises cortisol as a survival hormone – when in doubt, reproduction (the menstrual cycle) is ‘sacrificed’ in favour of stress management. This is because cortisol and the menstrual hormone progesterone share the same chemical precursor (pregnenolone).

In cases of chronic stress, the body ‘steals’ pregnenolone to produce cortisol. This results in a progesterone deficiency, which in turn leads to an imbalance in relation to oestrogen, exacerbating PMS, water retention, breast tenderness and mood swings.

Furthermore, high cortisol levels signal danger to the brain. The release of the regulating hormones (LH and FSH) is curtailed. Ovulation is delayed or fails to occur altogether. Periods become irregular or stop altogether (stress-induced amenorrhoea).

If cortisol levels remain chronically high, receptor resistance can develop despite cortisol’s anti-inflammatory effect, meaning that inflammatory messengers (prostaglandins), which trigger cramps during your period, act unchecked. Stress therefore often leads to more painful periods.

Cortisol during perimenopause and the menopause

During the perimenopausal and menopausal periods, the ovaries produce less oestrogen and progesterone: as the protective effect of oestrogen wanes, the body becomes more sensitive to cortisol.

Night-time cortisol spikes are a common cause of waking up during the night and can exacerbate hot flushes. Many women also report increased weight gain around the abdomen during this stage of life, which may be linked to changes in stress hormone regulation. High cortisol levels can block the conversion of thyroid hormones, leading to symptoms of an underactive thyroid (fatigue, hair loss, feeling cold), even though the thyroid gland itself is healthy.

As women are already at higher risk of osteoporosis, persistently elevated cortisol levels are particularly critical, as they further accelerate bone loss.

Interpreting cortisol levels correctly

The concentration of cortisol in the blood fluctuates enormously throughout the day and follows the body’s internal clock. In a healthy person who is awake during the day and sleeps at night, the typical curve looks like this:

In the morning (approx. 6.00–8.00 am): Cortisol reaches its peak. The body boots up its systems to become alert and ready for activity.

Throughout the day: Levels fall steadily.

Midnight (approx. 10.00 pm – midnight): Cortisol reaches its lowest point, allowing the body to wind down and sleep.

Typical reference ranges in serum (blood plasma)

The exact figures may vary slightly depending on the laboratory, but serve as a rough guide:

µg/dL (micrograms per decilitre)

How is cortisol measured?

Blood, saliva or urine samples are sufficient to measure cortisol levels. Anyone experiencing symptoms should always discuss this with their GP first. A hormone test is only carried out if there is reasonable cause for suspicion. If there is concrete evidence of a metabolic disorder, the GP’s surgery will usually refer the patient to an endocrinologist (a hormone specialist) to check the function of the adrenal glands or pituitary gland in detail.

Over-the-counter cortisol self-tests are also available for use at home. However, their results are often of limited value, as cortisol levels are subject to natural fluctuations and are influenced by numerous factors. Therefore, the interpretation of the results should always be carried out by a healthcare professional.

When should you have your cortisol levels checked by a doctor?

It is advisable to have your cortisol levels checked by a doctor if there is a suspicion of pathological over- or under-production.

The main warning signs are:

Signs of elevated cortisol levels (e.g. Cushing’s syndrome):

• Rapid weight gain around the abdomen and neck, with thin arms and legs, and a round ‘moon face’
• Thin skin, bruises, reddish stretch marks on the abdomen; muscle weakness in the legs
• Sudden high blood pressure or diabetes that is difficult to control

Signs of cortisol deficiency (e.g. Addison’s disease):

• Extreme, chronic fatigue and muscle weakness
• Noticeable darkening of the skin (even without sun exposure), particularly on the lines of the hands and scars
• Weight loss, nausea, chronically low blood pressure (dizziness) and a strong craving for salty foods
• If several of these symptoms occur at the same time and cannot be explained by stress or lack of sleep, it is advisable to see your GP.

Lowering cortisol: what helps?

To lower cortisol levels in the long term, you need to signal to your body that there is no imminent danger. This can be achieved through diet, lifestyle and targeted relaxation techniques:

• Breathing and relaxation techniques: Just 2–3 minutes of deep inhalation and prolonged exhalation (e.g. the 4-7-8 method) activate the vagus nerve, which can lower cortisol levels in the short term.
• Prioritise sleep: Adequate and regular sleep is one of the most important factors for a stable cortisol rhythm. Chronic sleep deprivation can contribute to persistently elevated levels. Reducing caffeine intake in the afternoon and evening is also advisable.
• Spending time in nature: Studies show that spending just 20 to 30 minutes in green spaces (‘forest bathing’) can measurably lower cortisol levels.
• Exercise: Moderate exercise (walks, yoga, light strength training) lowers cortisol. Please note: Very intense endurance training lasting too long (over 60 minutes) can raise cortisol levels.
• Keep blood sugar stable: Sharp fluctuations in blood sugar (caused by sugar and white flour) put the body under stress. Opt for complex carbohydrates, proteins and healthy fats.
• Drink plenty of water: Even mild dehydration can increase cortisol production.

In addition, there are specific nutrients such as magnesium, omega-3 fatty acids and vitamin C, which have a calming effect on the nervous system, inhibit inflammation and modulate the body’s stress response.

Do home remedies help to lower cortisol levels?

Many traditional home remedies can, to a certain extent, influence the stress hormone and help to lower cortisol levels:

• Calming teas: Teas made from chamomile, lemon balm, passion flower or lavender are traditionally used for relaxation and can have a calming effect on the nervous system.
• Warmth: A warm full bath or foot bath in the evening signals to the muscles and brain that it is time to relax.
• Activating the vagus nerve: Slow, conscious breathing with prolonged exhalation (e.g. 4 seconds in, 8 seconds out) and singing can activate the parasympathetic nervous system and dampen stress responses.
• Stay well-hydrated: A large glass of water can help – even mild dehydration can trigger stress responses in the body.
• Dark chocolate: Small amounts of dark chocolate (with a cocoa content of around 70% or more) can temporarily boost your sense of well-being and reduce your subjective perception of stress.

Cortisol too low: Is that even possible?

Although chronically low cortisol levels are less common than high ones, they must be taken very seriously from a medical point of view. This condition is known as adrenal insufficiency. As the hormone provides the body’s drive, a deficiency leaves the body running on empty, so to speak.

Typical symptoms include extreme, chronic fatigue; persistently low blood pressure accompanied by dizziness; weight loss; nausea; cravings for salty foods; and, in some cases, a noticeable darkening of the skin (Addison’s disease).

What triggers low cortisol levels?

The most common cause is the abrupt withdrawal of cortisone medication, which causes the body’s own production to cease. However, autoimmune disorders, problems with the regulatory glands in the brain, or a period of profound exhaustion following years of chronic stress may also be underlying causes.

Please note: As a severe deficiency can become life-threatening under stress, any suspicion of this condition should always be investigated by a doctor.