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
ACTH level is highest during: 
Select and explain. 
A. Early morning, B. Evening, C. Afternoon, D. Night
A: Early morning
Answer: A: Early morning 
Explanation: A i.e. Early morningACTH level is highest during early morningQ. About 75% of daily output occurs between 4 AM and 10 AM.Secretion is least in the evening. The biological clock responsible for diurnal variation of ACTH is located in suprachiasmatic nuclei of hypothalamusQ.