This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Adrenal, Subject name: Pharmacology
In the treatment of congenital adrenal hyperplasia due to lack of 21 b-hydroxylase, the purpose of administration of a synthetic glucocoocoid is: 
Select and explain. 
A. Inhibition of aldosterone synthesis, B. Prevention of hypoglycemia, C. Recovery of normal immune function, D. Suppression of ACTH secretion
D: Suppression of ACTH secretion
Answer: D: Suppression of ACTH secretion 
Explanation: In congenital adrenal hyperplasia, Due to decreased formation of steroids--> decreased feedback inhibition of ACTH. Thus more ACTH is formed which leads to adrenal hyperplasia-->exogenous steroids are given to suppress ACTH secretion.