Cortisol is a hormone that is produced by the adrenal glands. It is commonly referred to as a stress hormone due to its ability to trigger and fuel the “fight-or-flight” response. However, cortisol also plays key roles in several other processes within the body such as regulating blood pressure and your circadian rhythm. Reduced levels of cortisol (Addison's disease) may result in low blood pressure and fatigue. Whilst high levels of cortisol may be characteristic of Cushing's syndrome and can result in the growth of excessive hair on the body in women or erectile dysfunction in men. In both women and men it can result in a sudden increase in weight, especially focused on the midriff area.