cortisol
n. a corticosteroid hormone whose glucocorticoid activity increases blood sugar levels. Blood levels of cortisol in humans vary according to sleep–wake cycles (generally being highest around 9:00 a.m. and lowest around midnight) and other factors; for example, they increase with lack of sleep and during pregnancy but decrease with diseases of the liver and kidneys. Cortisol is considered the primary stress hormone: In response to stress or injury, blood cortisol levels, and therefore glucose levels, increase, as does blood pressure, whereas activity of the immune system decreases and release of inflammatory substances in the body is contained. Cortisol thus improves the body’s ability to manage stress and to repair itself, and, since 1963, it and its synthetic analogs have been administered in the treatment of chronic inflammatory and autoimmune disorders. Exposure to prolonged stress, however, can lead to
excessive levels of cortisol, which can have deleterious effects on the body (e.g., hyperglycemia). Cortisol has also been implicated in intrauterine growth retardation of the fetuses of pregnant women exposed to profound environmental stress (e.g., trauma, industrial or natural disasters). Also called hydrocortisone.