Structures of estradiol metabolites.  Top row from left: 17β-estradiol, estrone sulfate, and estrone glucuronide, second row 2-hydroxyestrone, estrone, and 16α-hydroxyestrone, third row: 2-methoxyestrone, 4-hydroxyestrone, 16α,17α-estriol, and 16β,17β-estriol, fourth row:  4-methoxyestrone and 16α,17β-estriol
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