2058
Injection of indomethacin , a nonselective COX inhibitor , on the day of ovulation and the following day decreased serum levels of progesterone , as did injection of the selective COX - II inhibitor NS - 398 .
 serum
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Anatomy 
Text: {0} 
Answer:
 serum