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: Pediatrics
Which of the following enzyme deficiency is the most common cause of Andrenogential syndrome? 
Select and explain. 
A. 3 b hydroxylase deficiency, B. 17 a hydroxylase deficiency, C. 21 a hydroxylase deficiency, D. Steroid sulfatase deficiency
C: 21 a hydroxylase deficiency
Answer: C: 21 a hydroxylase deficiency 
Explanation: 21 a hydroxylase deficiency is the most common cause of androgenital syndrome and its clinical manifestations depends upon the extent of enzyme deficiency. In less severe cases there is only masculinization due to increased androgen production (17 ketosteroids and testosterone). In severe cases, due to mineralocoicoid deficiency they can also present with salt wasting if untreated leading to life threatening volume depletion and shock. 11 beta hydroxylase deficiency is marked by salt retention (increase in 11 DOC) leading to hypeension, masculinization and an increase in 11 deoxycoisol. 17 alpha hydroxylase deficiency is marked by increased production of mineralocoicoids and decreased production of 17 ketosteroids and 17 hydroxycoicoids. Ref: Rapid Review Biochemistry By John W. Pelley, page 91-2