Cortisol is a steroid hormone produced by the adrenal glands. Whenever you experience something your body perceives as a threat, like a large dog barking at you, a chemical known as adrenocorticotropic hormone (ACTH) is released in your brain. This triggers your adrenal glands to release cortisol and adrenaline.
Cortisol is the main hormone involved in stress and the fight-or-flight response. This is a natural and protective response to a perceived threat or danger. Increased levels of cortisol result in a burst of new energy and strength.
In the fight-or-flight response, cortisol suppresses any functions that are unnecessary or detrimental to that response. During a fight-or-flight response, you can have: