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
Not a marker for hyperparathyroidism is - 
Select and explain. 
A. Increase in serum calcium, B. Increase in 24 hour urinary calcium excretion, C. Increase in serum calcitonin, D. Subperiosteal resorption of phalanges
C: Increase in serum calcitonin
Answer: C: Increase in serum calcitonin 
Explanation: markers include increased serum calcium, 24-hr urinary calcium , creatinine clearance, bone mineral density ( Harrison 17 pg 2383)