Due to the negative feedback loop of how hydrocortisone and corticosterone are produced endogenously, with an exogenous steroid prescription, the endogenous process comes to a halt. therefore is the exogenous steroid is then abruptly discontinued, the patient can experience acute adrenal insufficiency (Addison crisis), which can be fatal. so if the steroid administration must be stopped, then this must be a gradual process so that the adrenal cortex has time to restart endogenous steroid production.