27502
After 150 days of treatment , animals were euthanized , and tissue samples were harvested to evaluate androgen , estrogen , progesterone and melatonin receptor subunits ( AR , ER - alpha and ER - beta , PRA , PRB and MT1R , respectively ) .
 androgen, estrogen, progesterone, melatonin
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 androgen, estrogen, progesterone, melatonin