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
Which ion channel is effected in hypokalemic periodic paralysis? 
Select and explain. 
A. K+, B. Na+, C. CI-, D. Ca2+
D: Ca2+
Answer: D: Ca2+ 
Explanation: Hypokalemic periodic paralysis is due to calcium channel mutations. Hypokalemic periodic paralysis, in which serum potassium drops during a paralytic episode, is the most common of the inherited periodic paralyses. Ref Davidson 23rd edition pg 366