- Cortisol is a vital glucocorticoid hormone produced by the adrenal cortex, specifically the zona fasciculata of the adrenal glands.
- It plays a crucial role in regulating a wide range of physiological processes, including metabolism, immune response, blood pressure, stress response, and circadian rhythm maintenance. Often referred to as the “stress hormone,” cortisol is essential for survival, enabling the body to respond effectively to both physical and emotional stressors.
- Cortisol production is governed by the hypothalamic-pituitary-adrenal (HPA) axis. When the body perceives stress, the hypothalamus secretes corticotropin-releasing hormone (CRH), which prompts the anterior pituitary gland to release adrenocorticotropic hormone (ACTH). ACTH travels through the bloodstream to the adrenal cortex, where it stimulates the synthesis and release of cortisol. Once in circulation, cortisol exerts a negative feedback effect on the hypothalamus and pituitary to suppress further CRH and ACTH production, maintaining hormonal balance.
- One of cortisol’s primary functions is its role in glucose metabolism. It promotes gluconeogenesis (the production of glucose from non-carbohydrate sources such as amino acids and glycerol) in the liver, and reduces glucose uptake in muscle and adipose tissue, helping ensure a stable supply of glucose for critical organs, especially the brain. Cortisol also contributes to lipid metabolism by promoting the breakdown of fat and protein catabolism, particularly in muscle tissue, to provide substrates for energy production.
- Cortisol is a powerful anti-inflammatory and immunosuppressive agent. It inhibits the release of pro-inflammatory cytokines, reduces leukocyte migration, and suppresses the activity of immune cells. This makes it a key therapeutic agent in the treatment of autoimmune diseases, allergies, and inflammatory conditions such as asthma or rheumatoid arthritis, typically in the form of synthetic corticosteroids like prednisone or dexamethasone.
- In the cardiovascular system, cortisol helps maintain blood pressure by enhancing the sensitivity of blood vessels to vasoconstrictors such as epinephrine and norepinephrine. It also plays a role in fluid balance by modulating the effects of antidiuretic hormone (ADH) and influencing kidney function.
- Cortisol levels follow a distinct diurnal rhythm, peaking in the early morning (around 6–8 a.m.) to promote wakefulness and energy mobilization, and declining throughout the day to reach their lowest levels at night. This rhythm is regulated by the suprachiasmatic nucleus (SCN) in the hypothalamus and is crucial for maintaining normal sleep-wake cycles. Disruption of this rhythm—due to chronic stress, shift work, or jet lag—can contribute to fatigue, metabolic dysfunction, and mood disturbances.
- Abnormal cortisol levels are associated with several medical conditions. Cushing’s syndrome, caused by prolonged exposure to high levels of cortisol (endogenous or exogenous), leads to symptoms such as weight gain (particularly in the face, abdomen, and back), muscle weakness, hypertension, osteoporosis, and mood changes. On the other hand, Addison’s disease (primary adrenal insufficiency) results from inadequate cortisol production and is characterized by fatigue, weight loss, low blood pressure, and skin hyperpigmentation. Cortisol is also implicated in mental health conditions such as anxiety, depression, and chronic stress disorders.
