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
Most common cause of Conn's syndrome is - 
Select and explain. 
A. Adrenal hyperplasia, B. Adrenal carcinoma, C. Adrenal adenoma, D. Pituitary ACTH hypersecretion
C: Adrenal adenoma
Answer: C: Adrenal adenoma 
Explanation: Conn's syndrome is primary hyperaldosteronism caused by an adrenal adenoma producing aldosterone. It is characterised by low renin levels. Most people have hypeension due to sodium retention which may cause poor vision or headaches . Occasionally there may be muscular weakness, muscle spasms, tingling sensations , or excessive urination due to hypokalemia. Complications include cardiovascular disease such as stroke, myocardial infarction, kidney failure, and abnormal hea rhythms. Reference : page 780 Davidson's Principles and practice of Medicine 22nd edition