This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Fluid and electrolytes, Subject name: Medicine
Hyperkalemia can occur in all the following except- 
Select and explain. 
A. Cushing syndrome, B. Crush injuries, C. Renal failure, D. Intravascular haemolysis
A: Cushing syndrome
Answer: A: Cushing syndrome 
Explanation: The enhanced mineralocoicoid effect in Cushing syndrome is caused by occupation of the MR by the high concentration of coisol. Hypokalemia and metabolic alkalosis are more common in Cushing syndrome caused by ectopic ACTH production (90%) than in other causes of Cushing syndrome (10%) Ref Davidson 23rd edition pg 364