Cortisol is the body’s main stress hormone, which is produced in the adrenal glands, located adjacent to the kidneys. It is synthesized from cholesterol and acts through specific intracellular receptors to affect numerous physiologic functions, including glucose and blood pressure regulation. When the body experiences physical or emotional stress, the brain stimulates the release of cortisol. However, cortisol is more than a simple marker of stress levels, it is a vital component to proper functioning of the body.
Glucocorticoids
According to Jonathan Ashwell et al. in “Glucocorticoids in T Cell Development and Function,” steroids are small compounds derived from a common precursor, cholesterol. The corticoid steroids can be divided into mineralocorticoids and the glucocorticoids. Glucocorticoids have many functions, including resistance to stress, regulation of intermediary metabolism, and immunosuppressive and anti-inflammatory effects. Cortisol is considered the most important human glucocorticoid as it is essential for each living cell.
Mechanism of Action
Cortisol is released during periods of fasting, exercise, awakening and psychosocial stress. Nagisa Sugaya et al. in “Effect of Day-to-Day Variations in Adrenal Cortex Hormone Levels on Abdominal Symptoms” explain that cortisol release is highly irregular. Typically, cortisol secretions peak in the early morning and decline in the evening. The regulation of cortisol is a complex system that begins with the release of CRH by the hypothalamus, which then triggers the pituitary gland to secrete ACTH. ACTH is a precursor that prompts the adrenal cortex to produce more cortisol.
The Stress Response
As reported by Bessel van der Kolk in “Memory and the Evolving Psychobiology of Post Traumatic Stress,” stress can affect the body in a variety of ways. When you are faced with internal dilemmas or external threats, norepinepherine or epinepherine, the fight-or-flight hormones, are released. However, when stress is long-term and perceived as hopeless, the hypothalamus initiates a series of hormonal reactions resulting in the release of cortisol. This release of cortisol—or the defeat response—leads to lipogenesis, tissue breakdown, immune suppression and possible visceral obesity.
Primary Purpose
In “Cortisol Connection: Tips on Managing Stress and Weight,” C. Maglione-Graves et al. emphasize that energy regulation and mobilization are two critical cortisol functions. Cortisol regulates energy by selecting the type and amount of substrate that is needed to meet the body's physiological demands. Cortisol moves energy from fat fat stores and delivers it to starving tissues. During stress, cortisol provides the body with protein for gluconeogenesis, the conversion of amino acids into carbohydrates. It plays a role in the stimulation of fat breakdown from adipose tissue and serves as a mechanism to conserve glucose by inhibiting glucose uptake in the body.
Other Functions
According to Robert Sapolsky et al. in “How do Glucocorticoids Influence Stress Response?,” cortisol acts as an anti-inflammatory, anti-allergic agent, suppressing the immune system during times of physical and psychological stress. It repairs tissue, controls immune cell production, increases erythrocytes and promotes fluid and electrolyte balance.. Cortisol mediates the cardiovascular and metabolic stress response by increasing blood pressure, cardiac output, glucose uptake and fat depletion. Cortisol is important in growth, development and cognitive functioning.
References
- “Annual Review of Immunology”; Glucocorticoids in T Cell Development and Function; Jonathan Ashwell et al.; April 2000
- "BioPsychoSocial Medicine”; Effect of Day-to-Day Variations in Adrenal Cortex Hormone Levels on Abdominal Symptoms; Nagisa Sugaya et al.; March 2010
- "Harvard Review of Psychiatry”; The Body Keeps the Score: Memory and the Evolving Psychobiology of Post Traumatic Stress; Bessel van der Kolk; January/February 1994
- "ACSM’s Health & Fitness Journal”; Cortisol Connection; Maglione-Graves et al.; Sept./Oct. 2005
- “Endocrine Reviews”; How do Glucocorticoids Influence Stress Response? Integrating Permissive, Suppressive, Stimulatory, and Preparative Actions; Robert Sapolsky et al.; February 2000
