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
Earliest phenotypic manifestation of Idiopathic hereditary hemochromatosis is - 
Select and explain. 
A. Post prandial increase in serum iron concentration, B. Elevated serum ferritin level, C. Slate grey pigmentation of skin, D. Increased transferrin saturation
D: Increased transferrin saturation
Answer: D: Increased transferrin saturation 
Explanation: None