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
The commonest cause of primary amenorrhea with ambiguous genitalia in a female with 46XX chromosome : 
Select and explain. 
A. 21 hydroxylase def., B. 17 hydroxylase def., C. 11 hydroxylase def., D. Desmolase hydrolase def
A: 21 hydroxylase def.
Answer: A: 21 hydroxylase def. 
Explanation: A i.e. 21- hydroxylase deficiencyClassic 21 - hydroxylase deficiency is most common cause of ambiguous genitalia in new born (virilization) and primary amenorrheaQ. i.e. Pseudohermaphroditism of female childPrimary amenorrhea with VirilizationQ in females is in:- 21 - hydroxylase deficiency- 11 - Hydroxylase deficiencyTypesMain function ofenzymeMineralococoid(M)Glucocoicoid(G)AndrogenFeatures21- OH-deficiencyGlucocoicoid &Mineralocoicoidproduction U"l'* HypotensionQ(salt losing virilization)* VirilizationQ in females* Precocious pubey in femalesQ.11 hydroxylase-deficiencyGlucocoicoidproductionT.1.1,T* HypeensionQ* VirilizationQ in females* Precocious pubey in femalesQ.17- hydroxylasedeficiencyGlucocoicoid &Androgen production'1'.1,14* Male hermaphroditeQ* Primary atnenorrhea infemalesQ.* HypeensionQ3 - p-hydroxylasedeficiencyMineralcoicoid &glucocoicoidproduction..1,.1,T* Male hermaphrodite.