Cortisol is a steroid hormone that plays a key role in the body's stress response and regulation of metabolism, immune function, and blood pressure. It is produced by the adrenal glands in response to stress and is often referred to as the "stress hormone." High levels of cortisol in the body can have negative effects on health, including increased risk of anxiety, depression, weight gain, and cardiovascular disease. Research on cortisol often focuses on understanding its role in stress-related disorders and developing interventions to regulate its levels and improve health outcomes.