Cortisol works with certain parts of your brain to control mood, motivation, and fear. It keeps your metabolism and immune system healthy. Though widely known as the body’s main stress hormone, cortisol has a variety of effects throughout the body. This hormone:
- Manages carbohydrate, fat, and protein metabolism
- Keeps inflammation down
- Regulates blood pressure
- Increases blood glucose
- Controls the sleep/wake cycle
- Increases energy to handle stress (1)
Of all the systems in the body, the endocrine system is perhaps one of the most complex. Its massive network of hormone-secreting glands is involved in maintaining various aspects of all the other systems. Cortisol, a major component of the endocrine system, is controlled by the interactions of your hypothalamus, pituitary, and adrenal glands.
The hypothalamus, situated just above the brainstem that connects the spinal cord to the brain, is considered the body’s master switchboard since it controls the entire endocrine system by maintaining the body’s internal balance or homeostasis. It is also the link between the endocrine and nervous systems.
The pituitary gland, also situated just above the brainstem, is sometimes called the “master” gland of the endocrine system because it controls the functions of many of the other endocrine glands.
Cortisol is a steroid hormone or glucocorticoid. It is synthesized from cholesterol in the cortex of the adrenal glands which sit on top of your kidneys.
The hypothalamus, pituitary, and adrenal glands are known as the HPA axis which is one of the most important of the body’s systems through its ability to cross individual cell membranes. The HPA axis is our central stress response system involving both the endocrine system and the central nervous system. (2)
Glucocorticoids are powerful substances synthesized and secreted by the adrenal glands and were originally thought to help in the regulation of glucose metabolism. Studies now show there are many more functions to glucocorticoids including immune system regulation and fat metabolism. Glucocorticoids are part of the feedback mechanism in the immune system, which reduces certain aspects of immune function, such as inflammation. (3)
Cortisol helps mediate the major response mechanisms in the body. These are the stress response, glucose response, and inflammatory response.
Your body is continually responding to internal and external stressors. It processes this information and elicits a response by activating the sympathetic nervous system which releases cortisol via the HPA axis. Cortisol will be released for several hours after encountering the stressor after which systemic homeostasis returns to normal. Acute stress is adaptive and enables you to face emergencies through the flight or fight response whereas chronic stress is known to have deteriorating effects on your health. (2)
How The HPA Axis Works
The complex HPA pathway simply explained is this. The sympathetic nervous system response occurs almost immediately and results in the secretion of epinephrine and norepinephrine which cause changes like increased heart rate and perspiration. About 10 seconds later, the HPA axis is stimulated. The hypothalamus responds to elevated norepinephrine levels by secreting corticotropin-releasing hormone into the bloodstream. This hormone called CRF stimulates the pituitary gland to secrete a substance called adrenocorticotropic hormone (ACTH) which travels to the adrenal cortex triggering the release of cortisol. (4)
Under normal conditions, cortisol secretion during an acute stress response serves to mobilize glucose reserves stored in various organs for energy. Hyperglycemia, increased blood glucose, is the immediate result due to either reduced uptake of glucose by cells, reduced insulin sensitivity, or increased synthesis of glucose. Almost all tissues in the body have glucocorticoid receptors for this process. Other glucocorticoids help to inhibit pain, to slow down non–vital organ systems, and to promote the adaptive fight-or-flight response. (5)
Under abnormal conditions, such as during disease states when cortisol is chronically elevated (Cushing syndrome) or chronically depressed (Addison’s disease), the normal glucose response to stress may be compromised.
Cortisol is also a potent anti-inflammatory hormone that helps to prevent the widespread tissue and nerve damage associated with inflammation by regulating the body’s immune response.
First, the short-term increase in cortisol is pro-inflammatory, functioning to destroy antigens, pathogens, or foreign invaders which are acting as stressors to the body. The increase in cortisol mobilizes glucose to then help decrease inflammation thus allowing for the effective management of stress. (6)
The critical anti-inflammatory role of cortisol may be emphasized by the countless inflammatory disorders commonly treated with its synthetic pharmaceutical replacement, corticosteroids.
Normally a blood test is used to test cortisol levels. Salivary cortisol levels are thought to correlate well with the levels of free cortisol in blood. The adrenal stress index (ASI), a salivary test, is the preferred test for adrenal function and a well-accepted, noninvasive, reliable indication of cortisol levels. (7)
Stress is the major factor regulating cortisol levels during both acute and chronic episodes. When the body does not return to normal after a stressor episode, two situations may occur. Either cortisol levels remain unnaturally high, or the chronic stressor depletes the body’s cortisol to such low levels that other health issues may appear.
Tumors in the adrenal gland or in the brain’s pituitary gland can trigger your body to make too much cortisol. This can cause a condition called Cushing syndrome which can lead to:
- rapid weight gain
- skin that bruises easily
- pink stretch marks on your skin
- slow healing of cuts and bites
- muscle weakness (8)
Addison’s disease is caused by an autoimmune response, which occurs when the body’s immune system assaults organs or tissues. With Addison’s disease, the immune system attacks the cortex of the adrenal glands where cortisol is made. Other causes include injury or infection to the adrenals, amyloidosis, and genetic defects. Usually, the symptoms appear over time and include:
- craving for salty food
- loss of appetite
- patches of dark skin
- unexplained weight loss
- extreme tiredness (9)
Managing your stress as well as naturally decreasing your inflammation through diet and lifestyle choices, can help maintain cortisol levels. This can result in decreased chronic disease risk and improved wellness.