Cortisol is a steroid hormone produced by the two adrenal glands, which sit atop each kidney. This hormone is widely known as the “stress hormone” because its levels typically rise during periods of physical or psychological strain. Cortisol influences nearly every organ and tissue in the body, performing many functions beyond simply responding to stress. It plays a broad role in maintaining the body’s internal balance.
Cortisol’s Core Physiological Roles
Cortisol significantly influences how the body handles energy. It helps regulate the metabolism of glucose, fats, and proteins, ensuring the body has a steady supply of energy. For instance, cortisol stimulates the liver to produce new glucose from non-carbohydrate sources, a process known as gluconeogenesis, which helps maintain blood sugar levels between meals.
Cortisol also decreases inflammation. It suppresses substances that promote inflammation, acting as a natural anti-inflammatory. This helps calm excessive immune responses.
Cortisol regulates blood pressure. It influences blood vessel constriction and fluid balance, impacting blood pressure. This maintains cardiovascular stability.
Cortisol helps regulate the body’s sleep-wake cycle. Levels are highest in the morning, promoting wakefulness, and gradually decline throughout the day, reaching their lowest at night. This synchronizes the body’s internal clock.
Cortisol suppresses immune system activity. While beneficial for inflammation, prolonged suppression increases infection susceptibility. High levels also decrease new bone tissue production.
Cortisol’s Role in the Stress Response
Cortisol is a major component of the body’s acute stress response, often called the “fight-or-flight” mechanism. When faced with a perceived threat, the body rapidly releases cortisol along with adrenaline. This surge prepares the body for immediate action.
It provides a quick energy boost by stimulating the liver to release stored glucose. It also converts fats and proteins into usable energy, fueling muscles and the brain. This rapid energy mobilization helps an individual confront or escape danger.
Cortisol’s stress effects are temporary, aimed at short-term survival. Once the threat passes, levels return to baseline. This allows the body to conserve resources and recover.
Health Impacts of Cortisol Imbalance
Prolonged high cortisol, from chronic stress or conditions like Cushing’s syndrome, leads to health issues. It can cause high blood sugar, increasing type 2 diabetes risk. Excess glucose also contributes to abdominal weight gain.
High cortisol also weakens the immune system, increasing infection susceptibility. It decreases bone formation, potentially reducing bone density. Symptoms include fatigue, muscle weakness, and mood changes.
Conversely, insufficient cortisol (adrenal insufficiency or Addison’s disease) presents health challenges. This occurs when adrenal glands produce too little cortisol. Individuals often experience persistent fatigue, unexplained weight loss, and low blood pressure.
Other symptoms include muscle weakness, nausea, vomiting, and abdominal pain. Adrenal insufficiency requires medical intervention to replace missing hormones and manage symptoms. Both excess and insufficient levels disrupt the body’s balance and require careful management.
Natural Rhythms and Regulation of Cortisol
Cortisol levels fluctuate throughout a 24-hour cycle, following a circadian rhythm. Levels are highest in the early morning, peaking around 8 AM, promoting wakefulness. They gradually decline throughout the day and night, reaching their lowest around midnight or early sleep.
Cortisol regulation involves a complex feedback system in the brain and adrenal glands. The hypothalamus releases corticotropin-releasing hormone (CRH), signaling the pituitary gland to produce adrenocorticotropic hormone (ACTH). ACTH then stimulates the adrenal glands to release cortisol.
This pathway ensures appropriate cortisol release based on body needs and daily rhythms. However, medical conditions affecting adrenal glands or brain regulatory centers can disrupt this pattern. When imbalances are suspected, cortisol levels can be measured through blood, urine, or saliva tests to diagnose the issue.