A hydroxylated metabolite of ESTRADIOL or ESTRONE that has a hydroxyl group at C3, 16-alpha, and 17-beta position. Estriol is a major urinary estrogen. During PREGNANCY, a large amount of estriol is produced by the PLACENTA. Isomers with inversion of the hydroxyl group or groups are called epiestriol.

Synonyms: 16-alpha-Hydroxy-Estradiol, 16 alpha Hydroxy Estradiol, FB33469R8E, 16beta Hydroxy Estradiol, Ovestin, (16beta,17beta)-Estra-1,3,5(10)-Triene-3,16,17-Triol, 0, 8XZ32LI44K, 16alpha,17beta-Estriol, 16alpha,17beta Estriol, Estra-1,3,5(10)-Triene-3,16beta,17beta-Triol, (16alpha,17beta)-Estra-1,3,5(10)-Triene-3,16,17-Triol, Estriol, 16beta-Hydroxy-Estradiol, Estra-1,3,5(10)-triene-3,16,17-triol, (16alpha,17beta)-, Epiestriol