Pediatrics Endocrinology 731eeeea In congenital adrenal hyperplasia most common deficiency A 21- alpha hydroxylase deficiency B 11- beta hydroxylase deficiency C 17 - hydroxylase deficiency D 3 beta hydroxylase deficiency High-Yield Explanation Ans) a (21- alpha ) Ref Nelson 18'h ed p 2360More than 90% of CAH cases are caused by 21 -hydroxylase deficiency.