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
By which mechanism do LH and FSH return to baseline levels? 
Select and explain. 
A. LH surge, B. Negative feedback on gonadotropin-releasing hormone (GnRH) by progesterone, C. Negative feedback on GnRH by estradiol, D. Negative feedback on GnRH from testosterone
C: Negative feedback on GnRH by estradiol
Answer: C: Negative feedback on GnRH by estradiol 
Explanation: Just after the LH surge, estradiol levels increase, which causes negative feedback on GnRH to stop producing LH and FSH, resulting in the decrease in their levels