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: Pediatrics
Familial hypocalciuric hypercalcemia has mild elevation of calcium and PTH levels. It occurs secondary to what mutation? 
Select and explain. 
A. Missense mutation of mitochondrial calcium receptor, B. Missense mutation of ribosomal calcium surface protein, C. Missense mutation of Golgi complex receptor, D. Mutation of calcium - sensing receptor(CaSR)
D: Mutation of calcium - sensing receptor(CaSR)
Answer: D: Mutation of calcium - sensing receptor(CaSR) 
Explanation: None