A) refers to the expression of fewer receptors at the cell surface as part of a negative-feedback mechanism. B) refers to the decrease in cortisol secretion that occurs as an animal's metabolism slows down to its basal level. C) occurs in response to too little hormone reaching the target cells. D) is an idiopathic response to endocrine disrupters. E) occurs in response to the excretion of excess hormone by the kidneys.