BACKGROUND	We hypothesized that E+P would preferentially metabolize to 16-hydroxyestrone ( 16-OHE1 ) rather than 2-hydroxyestrone ( 2-OHE1 ) , and that breast cancer risk would be associated with baseline and 1 year changes in estrogen metabolites : positively for 16-OHE1 levels and negatively for levels of 2-OHE-1 and the 2:16 ratio .\