Introduction
The hypothalamic-pituitary-adrenal (HPA) axis is a major player in the stress response system and activation of this axis in response to stressors results in the release of adrenaline and glucocorticoids. This allows individuals to prepare for a “fight-or-flight” response and adequately cope with the stressor. However, studies have shown that different individuals vary in their responses to stress, and some are more susceptible to stress-related disorders than others. Strang and colleagues (2008) reported that women are more prone to mood and anxiety disorders than men this is because they produce more stress hormones than men. This is due to various factors which include biological factors, social and psychological factors. Some of the biological factors manifest themselves in situations like; postpartum, premenstrual and pregnancy periods. Among the social factors, women’s role strain in society and also abuses have been seen to be one of the major causes of stress. And at the same time, they found that older subjects (30-55) displayed higher stress response levels compared to a younger age group (18-30), through measurements of anxiety, hostility, and depression.
Past studies measuring the different responses in humans have relied on changes in plasma cortisol levels. This hormone is involved in stress and anxiety responses and through negative feedback in the HPA axis, cortisol levels are regulated by CRH and ACTH to maintain homeostasis. Dysregulation in cortisol levels has been linked to psychiatric disorders including depression and PTSD. For example, high cortisol levels have been linked to depression in patients, while low cortisol levels have been associated with post-traumatic stress disorder (PTSD) (Cooper, et al., 2005).
Also, cortisol is critical in physiological functions. According to Freeman (2002), cortisol in the blood causes harm when in high concentrations with high cases of high blood pressure and suppressed thyroid functions. Additionally, the high cortisol levels also result in reduced bone density, weakened cognitive performance and hyperglycemia. On the other hand, studies of cortisol have provided treatment for a variety of ailments. Through a synthesis of different forms of cortisol, diseases like rheumatoid arthritis have been treated using hydrocortisone.
Hence, we see that cortisol is indeed an important factor in neuroendocrine regulation, and dysregulation of this hormone can lead to behavioral, cognitive, and physiological changes.
Functions of cortisol
In our body, some of the main functions of cortisol are controlled/regulation of blood pressure, control of the cardiovascular functions, regulation of protein used in the body, metabolism of carbohydrates and fats. In its work, cortisol is known to cause some physiological effects like an increase in blood pressure, an increase in blood sugar by the release of insulin, and also lowering immune response (Freeman, 2002).
Cortisol has also been known to have has some anti-inflammatory effects on the human body. This is done through the reduction of the secretion of histamine and lysosomal membrane stabilization. The hormone also prevents secretion of the ACTH by inhibiting corticotropin-releasing hormone. This in effect triggers a negative feedback mechanism for ACTH. Studies have shown that damage to the hippocampus cells may result following prolonged exposure to high levels of cortisol, which gives rise to impaired learning. On the other hand, short-term cortisol exposure aids in the creation of memories (Nishiyama, Tlaygeh, Hejal & Arafah, 2007).
Chemistry of Cortisol
The systemic name of cortisol (hydrocortisone, C21H30O5) is 11Ăź,17,21-Trihydroxypregn-4-ene-3,20-dione and it has a molecular weight of approximately 362.47. Cortisol synthesis occurs from the precursor of all steroid hormones, the progesterone. In its conversion, C-11, C-17 and C-21 hydroxylation occur. The cortisol synthesis is stimulated by the adrenocorticotropic hormone (ACTH) in the adrenal gland. On the other hand, the hypothalamus corticotropin-releasing hormone (CRH) is responsible for stimulating the adrenal gland. The biological release of cortisol involves stimulation by the HPA axis which is stimulated by environmental stressors. The ACTH, despite controlling cortisol, acts by regulating the rate of calcium influx into the cortisol secreting target cells. In turn, the ACTH is controlled by the corticotropin-releasing hormone (CRH), a hypothalamic peptide that is controlled by the nervous system (Taylor, Grebe & Singh, 2004).
Measurement of Cortisol
Cortisol has been used by many psychologists and even scientists to give a measure of a human and even animal’s psychological health and even behavior. According to Taylor et al., (2004), essays on serum or even plasma cortisol are exceptionally helpful in the diagnosis of adrenal insufficiency and hypercortisolism. It is important however to determine the type of situation and sample to be used to test the levels of cortisol.
While deciding on the sample specimen to analyze, different samples used are blood serum, urine and saliva. However, different specimens have their pros and cons depending on the case at hand. For example, it has been reported that serum cortisol may be prone to effect by hormonal changes especially in women (Taylor et al., 2004). In addition, it only represents a small percentage (5%) of the total hormone available to the body tissues compared to saliva. Saliva specimen also has its drawbacks, for instance; shorter drug detection times, probability of false results due to changes in salivary PH brought about by over-secretion of saliva (Restituto et al., 2004). However, saliva has been deemed the most suitable for measurement since the hormonal concentration in the saliva represents the actual number of hormones available to the body’s tissues.
In addition, the cortisol concentration is not affected by the volume or flow of saliva. The saliva is also the best medium for easy access of cortisol by the cells due to the fact that the hormone diffuses well in water matrices. An example is a study that was done by Restituto et al. (2008). In this study they found out despite the high specificity that is produced by serum and saliva specimens, saliva was seen to be more sensitive than serum. Urine specimen on the other hand is not easy to analyze since it might require the collection of total daily urine. This may not be easy since one cannot be able to accurately measure the variations in cortisol production.
One of the measurements used to measure the amount of psychological stress is the Trier Social Stress Test (TSST). The TSST is a controlled procedure where different subjects are subjected to stress under laboratory conditions by the experimenter, so as to be able to compare the stress levels. These tests are used as simulations of different psychological and even physiological conditions known to cause various reactions in an individual (Cohen et al., 2009). Another is a measurement of cortisol out of a laboratory into the natural setting where an individual reacts to real-life situations. The TSST, however, is the best and normally used method since it provides consistency and accuracy of the test. Scientific methods normally applied to test for the cortisol level are serum cortisol measurement by RIA for levels of cortisol in the serum and the salivary cortisol EIA (Taylor et al., 2004).
Factors affecting measurement
In order to ascertain the cortisol concentrations in blood, the individual’s sex associated with bodily hormonal imbalances and blood sugar levels is determined. Depending on an individual’s health conditions such as elevated cholesterol, heart disease, fatigue and impaired cognitive performance, the results of the cortisol measurement will be varied (Chapman, Al-Musalhi, et al., 2006). In blood, the highest levels of cortisol concentration have been established to be in the early morning. Similarly, the lowest cortisol concentrations have been recorded at about 3 to 5 hours after the onset of sleep. Last but not least, another factor that influences the concentration of cortisol is the type of foods consumed. For instance, alcohol causes an increase in glucocorticoid levels by activating the HPA axis. On the other hand, coffee elevates the level of cortisol in turn aggravating stress. Lastly, bananas and artificial colored foods are known to raise cortisol levels (Chapman, Al-Musalhi, et al., 2006).
These changes in patterns of cortisol levels in serum have been studied in order to provide a relation with abnormal ACTH levels, psychological stress, and clinical depression (Chapman, Al-Musalhi, et al., 2006). It has also been used to test the effect of physiological stressors like illness, fever, trauma, pain, fear, or physical exertion. They have also been used as indicators and sensors of psychological stress in people and helped in the understanding of human reactions to different environments.
Conclusion
To conclude, cortisol is an important hormone in the human body in the regulation of the stress response axis. High cortisol levels have been reported in individuals with stress-related disorders and other psychological disorders. In addition, scientists have been able to find treatment through a similar understanding of the modes of the function of cortisol in the body. These treatments have been cleared through the manufacture of drugs from modification and synthesis of the cortisol hormone. However, it has also been found out that through this understanding psychologists have been able to help advise their patients on the effective ways to avoid and control stress by avoiding and minimizing cortisol enhancers.
References
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