Cortisol is a steroid hormone that belongs to the class of glucocorticoids. When used as a medication, it is known as hydrocortisone. Cortisol is primarily secreted by the adrenal cortex. It is released in a circadian cycle, with increased release under stress and low blood glucose concentrations. Its functions are mainly to increase blood glucose gluconeogenesis, suppress the immune system, and affect fat, protein, and carbohydrate metabolism. Increased cortisol can be seen in hypercortisolism, hypothyroidism, liver disease, asthma crisis, accidental hypothermia, feminization of men, and certain psychiatric patients. Decreases can be seen in diseases such as hypopituitarism. Patients with abnormal cortisol levels are advised to seek prompt medical attention.