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: Medicine
Increased Ca, decreased PO4. Diagnosi- 
Select and explain. 
A. Primary hyperparathyroidism, B. Secondary hyperparathyroidism due to Vit D deficiency, C. Malignancy, D. Osteoporosis
A: Primary hyperparathyroidism
Answer: A: Primary hyperparathyroidism 
Explanation: None