Glucocorticoids are frequently used for both diagnostic and therapeutic purposes. Their action mimics endogenous glucocorticoid actions by altering the activity of the hypothalamic-pituitary-adrenal (HPA) axis. Therefore, they can be responsible for iatrogenic diseases, particularly if used at high doses and for a long time. The aim of this brief review is to show the main pharmacological characteristics and the endocrine effects of glucocorticoids. The HPA axis insufficiency, related to acute glucocorticoid withdrawal, is also discussed.