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: Medicine
[{'content': 'New born 7 days old with vomiting and dehydration clinical examination was normal except for hyperpigmentation of nipple. Electrolytes Na: 120 meq. K: 9 meq. mostlikelydiagnosis - \nSelect and explain. \nA. Primary hypothyroidism, B. Cong, adrenal hyperplasia, C. Panhypopituitarism, D. Pyloric stenosis', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Congenital adrenal hyperplasia due to defect in CYP21A2 is suggested by episodes of acute adrenal insufficiency with hyponatremia , hyperkalemia , dehydration & vomiting ( Harrison 17 pg 2267)', 'role': 'assistant'}]