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: Physiology
Which of the following hormones exerts the least effect on calcium metabolism of bone tissue? 
Select and explain. 
A. Androgen, B. Estrogen, C. Nor epinephrine, D. Thyroid hormone
C: Nor epinephrine
Answer: C: Nor epinephrine 
Explanation: None