This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Endocrinology, Subject name: Pediatrics
Pseudohermaphroditism in a female child is most commonly due to 
Select and explain. 
A. 21- hydroxylase deficiency, B. 17-hydroxylase deficiency, C. 11-hydroxylase deficiency, D. 3-hydroxylase deficiency
A: 21- hydroxylase deficiency
Answer: A: 21- hydroxylase deficiency 
Explanation: Excess androgen production is the most common cause of disorder of sexual differentiation (pseudohermaphroditism) mainly 21- hydroxylase deficiency. Others are 11- beta-hydroxylase and 3 beta-hydroxysteroid dehydrogenase deficiency Image : Female pseudohermaphroditism with normal uterus. A, Sonographic view of the external genitalia; note the enlarged clitoris (C) with fused prominent labia (L). B, The corresponding postnatal disposition verifying enlarged clitoris and fused labia. Reference: Ghai essential of paediatrics, eighth edition, p.no:538