Maintenance of life depends on the organism’s appropriate response to a stressor. One of the major response reactions to stress is facilitated by the hypothalamus-pituitary-adrenal (HPA) axis. A cascade of endocrine reactions from hypothalamus and pituitary culminates in release of glucocorticoid hormones from the adrenal gland. The main glucocorticoid hormone in humans is cortisol. A negative feedback loop exists where cortisol suppresses further release of hormones (see Figure). Cortisol is present in our body throughout the entire day, with the highest levels shortly after waking time and the lowest levels at night. Additional cortisol is released during a stress response, acting thereby as a major biomarker for stress. Main functions of cortisol are regulation of metabolism through increase of blood glucose and suppression of the inflammatory immune response. It is also involved in further processes such as regulation of salt and water balance, bone formation, memory formation, and foetal respiratory system maturation.
An instant physiological response to an acute stressor is vital when facing a potential life threat. A chronic stressor, such as chronic disease, sustained high work load, or untreated psychological trauma, however, leads to a prolonged activation of the HPA axis or errors in the feedback loop, which triggers changes in the system. A dysfunctional HPA axis (congenital or acquired) is often associated with development of diseases. Hyperfunction leads to conditions with increased cortisol levels, such as Cushing’s syndrome, and is linked to increased susceptibility to infections, psychosomatic and psychiatric disorders, such as depression or anorexia nervosa. Hypofunction of the HPA axis, and therefore decreased cortisol levels, is associated with conditions such as Addison’s disease, autoimmune disorders (e.g. multiple sclerosis or rheumatoid arthritis), chronic fatigue, fibromyalgia, neurodermatitis, or asthma.
Exposure to stress can also cause or intensify diseases. Chronic stress, in particular, is linked to the development of cardiovascular disease, diabetes, metabolic syndrome, hormonal imbalance or cancer, which in turn can serve as a stressor, creating a vicious circle.
Further averse chronic factors such as smoking, unhealthy lifestyle, continuous work overload, long-term unemployment, or sleep deprivation have also been linked to disturbed HPA axis function. Avoiding such stressors and introduction of balanced diet, active lifestyle and stress management activities (e.g. mindfulness, yoga or exercise) may help to restore cortisol levels and increase resistance to diseases.
Measuring cortisol levels in an individual is therefore a useful tool to monitor performance and diagnose diseases. LIH PhD student Ksenia Trischel is currently developing a novel non-invasive method for cortisol collection and measurement.