Down-regulation is: (A) Increased destruction of a hormone, (B) Feed back inhibition of hormone secretion, (C) Decreased concentration of a hormone in blood, (D) Decrease in number of receptors for a hormone
Answer is D. Downregulation: An decrease in the number of receptors on the surface of target cells, making the cells less sensitive to a hormone or another agent Downregulation of receptors happens when receptors have been chronically exposed to an excessive amount of hormone Ref : Biochemistry by U. Satyanarayana 3rd edition Pgno : 428