Glucocorticoids (or, less commonly, glucocorticosteroids) are a class of corticosteroids, which are a class of steroid hormones. Glucocorticoids are corticosteroids that bind to the glucocorticoid receptor that is present in almost every vertebrate animal cell. The name "glucocorticoid" is a portmanteau of "glucose", "cortex", and "steroid", referring to its role in regulating the metabolism of glucose, its synthesis in the adrenal cortex, and its steroidal structure.
Glucocorticoids are part of the feedback mechanism in the immune system, which reduces certain aspects of immune function, such as inflammation. They are therefore used in medicine to treat diseases caused by an overactive immune system, such as allergies, asthma, autoimmune diseases, and sepsis. Glucocorticoids have many side effects, including adverse drug reactions. They also interfere with some of the abnormal mechanisms in cancer cells, so they are used in high doses to treat cancer. In particular, they inhibit lymphocyte proliferation, which is significant for lymphomas and leukemias. They can also lessen some side effects of chemotherapy (anticancer drugs).