Whether a result of an upcoming deadline at school or problems with financial responsibilities, stress is a common part of life.

Cortisol is a hormone that is responsible for regulating the body’s daily fluctuations of stress. The body adapts to environmental and internal stressors “based on need,” according to Dr. John Konhilas, who received his Ph.D. in physiology from the University of Illinois at Chicago and is currently an associate professor of physiology at the UA. Abnormal amounts of stress, however, can cause serious problems with the natural functions and behaviors of the human body.

The Natural Rhythm

Hormones are regulatory chemicals that are produced in specialized glands and transported through the bloodstream to target specific organs and tissues. These powerful substances can control the body’s day-night cycle—called circadian rhythm—which regulates bodily functions, like wakefulness.

Much of this rhythm is controlled by a small part of the brain called the hypothalamus, which controls the release of hormones and ensures that all of the body’s systems are properly regulated. A slight imbalance in this internal clock can lead to negative consequences.

Cortisol begins to build up overnight and peaks around 8 a.m., according to Douglas Keen, a senior lecturer in the department of Physiology. Cortisol slowly declines throughout the rest of the day. It is natural for cortisol to be secreted in response to physical stress, such as intense exercise or a “fight or flight” situation. The hormone, however, should return to its normal pattern afterward.

The problem is that a high-stress lifestyle does not allow cortisol to return to natural levels after a stressful event, according to the Mayo Clinic. This elevates the starting point of the circadian rhythm.

A Fight with the Enemy

Prolonged levels of high cortisol can cause health problems, including sleep disruption, impaired cognitive ability, blood-sugar imbalance, weakened immune function and high blood pressure.

Stress can affect a sleep hormone called melatonin, which is regulated by levels of light and peaks at night to make the body drowsy. The body can be willed to push through this innate desire with caffeine or other substances, but doing so will reset the peak of melatonin on the circadian rhythm to a different time. The sleep cycle is now temporarily changed until the brain can reset itself.

College students are one of the most sleep-deprived populations, according to Campus Mind Works, an online resource created by the University of Michigan Depression Center. Sleep deprivation can translate to difficulty with the cognitive processes of applying and generating new knowledge. Information is solidified during the sleep cycle, which increases long-term retention of new material, according to Keen. Proper sleep is necessary to learn. Research has also shown that sleep deprivation can lead to high cortisol levels.

Those all-nighters are a lose-lose for college students.

Another function of cortisol is to raise blood sugar for a boost of energy in a “fight or flight” situation. Yet, prolonged high levels of this stress hormone can decrease insulin sensitivity, which can lead to diabetes and abdominal weight gain.

The immune system is also weakened during times of increased stress levels. Inflammation is caused when the body tries to fight off a pathogen. Cortisol has an anti-inflammatory effect, counteracting this defense process. Humans can become vulnerable to disease after consecutive days of elevated cortisol levels.

“[Students] are more likely to get a cold going into exam week,” Keen said.

High blood pressure can be a long-term outcome of elevated cortisol levels in the bloodstream. Vessels constrict to stop the unnecessary blood from entering the extremities, sending it to other body parts, such as the kidneys. The kidneys receive 20-25 percent of the oxygenated blood to filter waste at a normal blood pressure, according to Konhilas. This percentage increases to about 30-40 percent with high blood pressure. An increase in pressure due to stress stretches the organ’s vessels and can cause long-term damage to the kidneys. The damage can affect the ability of the kidney to remove waste and excess fluid.

This may sound like an extreme effect of prolonged stress, yet high blood pressure is the second leading cause of kidney failure in the U.S., according to the National Institute of Diabetes and Digestive and Kidney Diseases.

Defeating the Foe

A normal exercise routine and sleep cycle can help alleviate the levels of cortisol in the bloodstream. Exercise is a physical release of the cortisol hormone and allows the levels to return to a normal rhythm, according to Keen. A temporary increase in cardiac output helps with regulation of blood-glucose levels, enhancing the insulin receptor pathway for up to 24 hours after physical activity. An elevated heart rate during exercise allows extremities to receive the required blood flow to continue their correct function. This condition turns into a high blood pressure problem when the cardiac output stays elevated at rest.

Keen referred to the maintenance of these natural systems in order to lead a long and healthy life the “old use-it-or-lose-it phenomenon.” An understanding of this biological clock and its functions help researchers develop treatments for sleep disorders and other health problems, as well as procedures for stress management.

Follow Kaitlyn Fletcher on Twitter.