This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Female Reproductive System, Subject name: Physiology
What accompanies sloughing of the endometrium during the endometrial cycle in a normal woman? 
Select and explain. 
A. An increase in progesterone, B. The LH "surge", C. A decrease in both progesterone and estrogen, D. An increase in estradiol
C: A decrease in both progesterone and estrogen
Answer: C: A decrease in both progesterone and estrogen 
Explanation: At the end of the luteal phase, the corpus luteum is resorbed and fails to produce progesterone and estradiol, making levels fall precipitously and causing the endometrium to slough.