We all have cortisol in our bodies. Cortisol is a hormone that is released from the adrenal glands in response to stress, such as fear, anger, or boredom. Cortisol is released in times of duress to help us fight or run from danger. It increases blood sugar levels and suppresses the immune system. Studies have shown that cortisol levels in athletes increase before and after a competition. These levels can be used to predict the likelihood of injury. The release of high levels of cortisol before a competition, combined with increased physical exertion, can lead to muscle damage or other injuries.