15680
Serum levels of 25 - hydroxyvitamin D and the CYP3A biomarker 4 beta - hydroxycholesterol in a high - dose vitamin D supplementation study .
 25 - hydroxyvitamin D, 4 beta - hydroxycholesterol, vitamin D
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 25 - hydroxyvitamin D, 4 beta - hydroxycholesterol, vitamin D