This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Physiology
Down regulation of hormone means ? 
Select and explain. 
A. Decreased secretion of hormone, B. Decreased affinity to receptors, C. Defective regulation in secretion, D. Regulation by low concentration of hormone
B: Decreased affinity to receptors
Answer: B: Decreased affinity to receptors 
Explanation: Ans. is 'b' i.e., Decreased affinity to receptors Down regulation is a mechanism in which a hormone decrease the number or affinity of its receptors in target tissues. Down-regulation may occur by decreasing the synthesis of new receptors, by increasing the degradation of existing receptors or by inactivating receptors. The purpose of down-regulation is to reduce the sensitivity of the target tissue when hormone levels are high for an extended period of time.