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Estrogen receptor - alpha ( ER alpha ) is crucial for the adaptive response of bone to loading but the role of endogenous estradiol ( E2 ) for this response is unclear .
 Chemical: Estrogen; Chemical: estradiol
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
 Chemical: Estrogen; Chemical: estradiol