As the trail begins to curve, you stop for a second, close your eyes, tilt your head back, and breathe in as much fresh air in one breath as you can. As you begin your long exhale and open your eyes, you hear what sounds like teeth clacking. As you regain focus, your brain registers an 8-foot-tall, 900-pound grizzly bear in the middle of the dirt trail ten feet ahead.
Your body immediately responds with an increase in the hormones, adrenaline, and noradrenaline, which increase your heart rate, feeding more blood, oxygen, and energy into your body. Your breaths become rapid and shallow, allowing you to take in more oxygen for your muscles. Your digestion stops, your pupils dilate, making your vision much sharper, and your hearing is enhanced.
You aren't moving, but your muscles tense up, like a Ferrari in neutral with the engine revving. The pain in your back is completely gone. The first thing the bear notices is how pale your skin is, and he wonders if that will affect your taste. Your hands and feet become cold as blood is redirected to your muscles, brain, legs, and arms. Your mind is active, and your thoughts are racing. Your body is experiencing the acute stress response, also known as the "fight or flight" response–“The body’s natural physiological reaction to stressful, frightening, or dangerous events.” Your body releases cortisol, which helps you stay on high alert and triggers the release of glucose from your liver for quick energy.
When you face a threat, your brain and adrenal glands release hormones that trigger bodily changes that help prepare you to meet the threat. Adrenaline and noradrenalin continue to be released in short bursts during the threat but are broken down in minutes. For your body to continue having an improved ability to respond to stress, you release cortisol, the primary stress hormone. When the threat is gone (the bear walks away), your body breaks down the stress hormones, and the stress response ceases.
Stress Responses Can Be Life-Saving or Life-Threatening
Stress is a state that threatens our body's natural physiological balance. Your body reacts to physical and mental strain by activating hormonal circuits, which allows the body to deal with the stress and re-establish balance and equilibrium. If you perceive the stress as too intense or lasting too long, the stress response does not resolve, and you will not obtain equilibrium. If this maladaptation to stress is not resolved, it can lead to illness.
While the fight-or-flight stress response is critically important for survival, it is designed to be short-lived. Chronic stress can potentially last many weeks and be detrimental to your health. In addition, ongoing stress can interfere with your productivity, relationships, and health.
Potential symptoms related to chronic stress are:
- Aches and pains
- A change in social behavior and isolation
- Low energy
- Unfocused or cloudy thinking
- Change in appetite
- Increased alcohol or drug use
- Difference in emotional responses to others
- Emotional withdrawal
Chronic stress triggers include significant life changes, long hours, debt, troubled relationships, and chronic pain. In addition, the COVID-19 pandemic has substantially increased the stress level of Americans, disrupting work, education, health, care, and the economy, and will continue to do so.
Chronic stress can leave you feeling fatigued and run down, lowering immunity and making infections more likely and symptoms more severe. When stressed, you are more likely to engage in behaviors that may increase your risk of developing cancer. Behaviors include poor diet and obesity, smoking, decreased exercise, and alcohol use.
Increased Cortisol: The Good, The Bad, and the Ugly
Your body’s response to stress is regulated by the interaction between the hypothalamus, pituitary gland, and adrenal glands, or the HPA axis. Once your body establishes something as a threat, sensory information is sent to the amygdala, a part of the brain that processes emotion. If the amygdala interprets the signals and perceives danger, it activates the brain's hypothalamus. Three essential aspects of the HPA axis include:
- The hypothalamus releases corticotropin-releasing hormone (CRH) when it receives a stress signal from the amygdala.
- The pituitary gland releases adrenocorticotropic hormone (ACTH) into the bloodstream when CRH reaches it.
- ACTH binds to receptors, releasing cortisol, the primary stress hormone.
The HPA stress response is inactivated, and hormones are broken down once the threat has passed. In addition, physical and psychological stressors trigger the HPA axis, which can lead to chronic stress.
Some amount of stress and cortisol release is healthy and beneficial. For example, our cortisol level is highest upon waking, which helps us wake from a sleepy state. Also, low stress can help you be safer, more alert, and more motivated to achieve relationship and work goals. Mild stress can also be helpful for individuals in completing tasks and improving cognitive performance.
Because virtually all body tissues have glucocorticoid receptors, cortisol can affect almost all organ systems, including the nervous, immune, cardiovascular, respiratory, and musculoskeletal systems. These are the bodily systems that are of benefit for survival in acute stressful situations. Cortisol has many functions, including:
- Regulating the body's stress response
- Suppressing inflammation
- Regulating blood sugar
- Helping to control the sleep-wake cycle
However, when cortisol is too high, you will feel stressed frequently, have more unpleasant symptoms, and have a decreased sense of well-being.
The consequences of long-term increased cortisol include:
- Mood changes
- Impaired regulation of blood sugar
- Memory problems
- High blood pressure
- Increased risk of cardiovascular disease
- Increased body fat mass
Stress and Increased Cortisol Decrease Testosterone
When cortisol levels spike in response to stress, your body goes into “fight or flight" mode, and testosterone secretion ceases (testosterone-related reactions such as aggression and competition are unnecessary). During these times, the body optimizes muscles and hormones that aid in the survival reaction.
Research indicates that under stressful conditions, cortisol acts to suppress testosterone production. Increased cortisol levels suppress endocrine signaling, leading to decreased testosterone. In addition, studies show that increased cortisol directly inhibits testosterone production by inhibiting the Leydig cells in the testes.
Decreased testosterone can lead to many adverse health effects, including decreased libido, lower bone density, muscle mass decline, and increased fat production.
After adjusting for other factors, studies show that an increased cortisol level relative to testosterone level increases the incidence of coronary heart disease. The incidence of all-cause mortality, ischemic heart disease mortality, and incidence is positively associated with increased cortisol: testosterone ratio.
Behavioral Response: Cortisol vs. Testosterone
Testosterone regulates sexual behavior but is also involved with social behavior and cognition. Behaviors encouraged by testosterone include mating, competition, and aggression. Testosterone levels are reduced in response to psychological, physical, and acute (e.g., surgery) stress. The processes in the body that regulate cortisol and testosterone levels are antagonistic. For example, when you are in critical danger, there are benefits for survival with increased cortisol, but testosterone production ceases. During a fight or flight response, testosterone has no survival benefit.
A recent study found that testosterone encourages men's competitive behavior, but this depends on cortisol levels. In addition, chronically elevated cortisol levels can cause impotence and decreased libido by inhibiting testosterone production in men.
A study suggests that high levels of cortisol block testosterone's influence on competition and domination. When cortisol is released into the bloodstream during the stress response, the body is mobilized to escape danger.
Conversely, since cortisol and testosterone have an inverse relationship, testosterone limits the stress response. Testosterone appears to reduce fear behavior and reduce cortisol reactivity to stress. In addition, a study suggests that testosterone decreases social anxiety and may help modulate the effects of stress in socially challenging circumstances. Finally, studies show that testosterone replacement therapy improves depressed mood in older patients with low testosterone levels, affecting stress levels.
Personality traits appear to influence testosterone levels. In a study of 58 male medical students, salivary testosterone levels were measured at baseline and under stress. The study analyzed whether personality type influenced the results. Extraversion, aggression, and emotional inhibition led to a 28% change in salivary testosterone levels under stress. The study demonstrated that salivary testosterone level is influenced by personality traits and emotional control variables, which modulate the effects that stress has on an individual's biological responses.
The release of cortisol in response to stress is essential in adapting to the stressors. However, when we cannot cope with stress, chronic stress becomes harmful. Testosterone is directly reduced by increased cortisol related to stress. Chronic diseases such as obesity and type 2 diabetes contribute to poorer health and are associated with low testosterone. In addition, chronic stress and decreased testosterone levels are related to mental health complications, such as chronic fatigue, anxiety, and depression. Testosterone replacement therapy may reduce stress levels by improving physiological and mental health problems related to low testosterone.