Stress, slow to heal wounds, osteoporosis and being overweight are just a few signs of excess cortisol. Cortisol is referred to as the "stress hormone" because stress leads to an increase in cortisol levels. A high cortisol level can now be associated with various other diseases. For example, cortisol plays a role in diabetes mellitus, being overweight, obesity, and depression. In the following text the "stress hormone” will be explained in more detail along with the positive and vital functions of cortisol.


Cortisol is a hormone and belongs to the glucocorticoids group. Glucocorticoids are formed in the adrenal cortex and affect sugar metabolism. In addition to cortisol, cortisone belongs to the natural glucocorticoids. The majority of cortisol is in the blood in the bound form. Only 1-3% of cortisol is unbound in the blood plasma. Unbound cortisol is the active form of cortisol. Overall, the cortisol level, especially that of the free cortisol, is subject to fluctuations. Thus the level is highest in the morning, decreases over the course of the day, and has reached its minimum by around midnight [1]. The following graph shows the possible fluctuations of a cortisol level. Here, a cortisol level measurement is shown via a saliva profile. This will be discussed further under testing of cortisol levels.

Cortisol levels depend on age, sex, estrogen levels, stress, diet (especially a carbohydrate-rich diet), being overweight, and blood sugar levels. For example, during the menstrual cycle, pregnancy or menopause, women show much higher cortisol levels than men of the same age. During pregnancy the cortisol value can be increased a hundredfold [2].

Functions of cortisol in the body

Cortisol has vital functions for our bodies. It regulates physiological processes such as energy metabolism, the maintenance of mineral balance and blood pressure, the immune system, the treatment of stress, cell division, memory regulation, and brain function[1]. Cortisol has, for example, a vital function in carbohydrate delivery. At night it causes blood sugar to increase so that the body (with the lack of food supply between dinner and breakfast) has enough energy available. In addition, increased protein and fat metabolism, to provide energy, is stimulated by cortisol. Cortisol thus has a breaking-down (catabolic) effect, since both fatty tissues and muscles are broken down. Furthermore, the cortisol hormone has an effect on the immune system. Simply put, it is responsible for treating the damage caused by the immune system. Synthetically produced glucocorticoids such as prednisone are thus used, for example, in autoimmune diseases, in which the immune system attacks the body’s own healthy tissue. It is also used in allergic reactions and for chronic and acute inflammations [3].

Symptoms of cortisol deficiency

A lack of free cortisol in the body can have many causes. In the case of renal insufficiency (sub-function), the cortisol level is reduced due to lack of formation. This condition is called Addison's disease. This may cause weakness and fatigue, changes in the skin, weight loss, vomiting and reduced blood pressure. Also, if accompanied by cortisol deficiency, it may cause carbohydrate and calcium metabolism disorders, changes in the psyche and loss of stress management, in addition to the other symptoms. [4].

Symptoms of excess cortisol

A heightened cortisol level can be identified not only via the suspension or displacement of the physiological daily rhythm described above, but also via individual heightened values. For example, excess cortisol prevents skin wounds from healing. An increased cortisol level also prevents the incorporation of nutrients into the bones, leaving them vulnerable to demineralisation (degradation of bone mineral) and osteoporosis. In the case of osteoporosis, the bones become softer and so can become more easily deformed and break faster. Furthermore, several studies have shown a cortisol excess in patients with depression. This suggests that cortisol may have an effect on depression. A cortisol excess can be caused, for example, by diseases such as Cushing's disease or tumours. Cushing's disease is caused by a tumour in the pituitary gland (a hormonal gland in the brain) and causes an increased cortisol release. Signs of Cushing's syndrome include weight gain, skin changes, hypertension, and increased blood sugar. Cushing's syndrome can also be caused by medications such as synthetic glucocorticoids [3].

Testing of cortisol levels

The cortisol level is usually determined using a daily profile. The test determines the concentration of the stress hormone cortisol in saliva. A daily profile uses several measurements across the course of one day to illustrate how your cortisol level changes over this period. This is much more accurate than taking a single measurement. Key to this is that over the course of a day your cortisol level is subject to significant physiological variations. Due to current lifestyles increasingly involving professional and personal stress, cortisol levels often lie outside the normal range. In addition, various medical conditions and medications can lead to deviations in cortisol levels. The cerascreen® Cortisol Test helps you measure your cortisol levels and provides you with a comprehensive report with recommendations for action and health tips.

Cortisol and diabetes

Long-term elevated cortisol levels can lead to diabetes mellitus. Diabetes mellitus is a blood sugar disorder. Impaired insulin production leads to fluctuations in the blood sugar level [2].

In a stressful situation the cortisol level increases and leads to increased sugar release. The blood sugar level increases [3]. Increased insulin is then distributed by the pancreas to lower the blood sugar to a normal level. If the pancreas has to permanently fight against heightened blood sugar levels, this can lead to diabetes in the long-term. The receptors which process insulin react with increasingly less sensitivity due to their frequent oversupply of insulin. Insulin resistance can arise and develop into type 2 diabetes mellitus.[5].

Cortisol and stress

The cortisol level is highly dependent on stress. Acute diseases, operations, or psychological trauma may increase cortisol levels, among other things[1]. Stress (especially mental stress) can have a negative impact on mental performance and memory. This is caused by long-term elevated cortisol levels. Normally, the brain perceives the stress and releases its response the moment there is a physical or perceived threat. The resulting cortisol is distributed via various mechanisms. Cortisol subsequently provides the physical resources to deal with the acute stress situation. These resources are energy reserves, such as carbohydrates, fats and proteins. Under sustained stress, however, there is more demand on resources, which ultimately leads to a shortage in the brain and may cause the above symptoms to occur [6].

Cortisol and excess weight

Elevated cortisol levels and being overweight are often connected. A large-scale study of 160,000 professionals identified a positive correlation between a high cortisol level and excess weight[7]. This may be due to higher stress levels in overweight individuals. An elevated cortisol concentration can also lead to changes in the fat cells. Thus, the fully developed fat cells (adipocytes) are formed from the precursors to the fat cells (pre-adipocytes). In contrast to the pre-adipocytes, the adipocytes have a fat-storing function. This can lead to weight gain[8].


1 Gatti et al. (2009). Cortisol assays and diagnostic laboratory procedures in human biological fluids. Clinical Biochemistry. 42: 1205-1217.
2 De Sanctis et al. (2015). Cortisol Levels in Central Adrenal Insufficiency: Light and Shade. Pediatric Endocrinology Reviews. 12 (3): 213-219.
3 Heinrich et al. (2014). Biochemie und Pathobiochemie [Biochemistry and Pathobiochemistry] (9th edition). Berlin Heidelberg: Springer Verlag.
4 Kaiser & Kley (2002). Cortisontherapie [Cortisone Therapy] (11th edition). Stuttgart: Georg Thieme Verlag KG.
5 Kasper, H., & Burghardt, W. (2014). Ernährungsmedizin und Diätetik [Nutritional Medicine and Dietetics] (Vol 12). Würzburg: Urban & Fischer.
6 Shields et al. (2015). Does cortisol influence core executive functions? A meta-analysis of acute cortisol administration effects on working memory, inhibition, and set-shifting. Psychoneuroendocrinology. 58: 91-103.
7 Nyberg et al. (2012). Job strain in relation to body mass index: pooled analysis of 160 000 adults from 13 cohort studies. Journal of International Medicine. 272: 65-73.
8 Incollingo Rodriguez et al. (2015). Hypothalamic-pituitary-adrenal axis dysregulation and cortisol activity in obesity: A systematic review. Psychoneuroendocrinology. 62: 301-318."