<unk> , or simply<unk> , also known as 16α-hydroxy-17α-estradiol or estra-1,3,5(10)-triene-3,16α,17α-triol, is a minor and weak endogenous estrogen, and the<unk> -epimer of estriol (which is 16α-hydroxy-17β-estradiol). It is formed from 16α-hydroxyestrone. In contrast to other endogenous estrogens like estradiol,<unk>  is a selective agonist of the ERβ. It is described as a relatively weak estrogen, which is in accordance with its relatively low affinity for the ERα.<unk>  has been found to be approximately 400-fold more potent than estradiol in inhibiting tumor necrosis factor α (TNFα)-induced vascular cell adhesion molecule 1 (VCAM-1) expression in vitro. Relative affinities (%) of<unk>  and related steroids Compound Estradiol 2.6 7.9 100 0.6 0.13 8.7 <0.1 Alfatradiol <1 <1 15 <1 <1 ? ? Estriol <1 <1 15 <1 <1 ? ? 16β-Epiestriol <1 <1 20 <1 <1 ? ?<unk>  <1 <1 31 <1 <1 ? ? Values are percentages (%). Reference ligands (100%) were progesterone for the , testosterone for the , for the , for the , aldosterone for the , for , and cortisol for .
17α-Epiestriol
3β-Androstanediol
3α-Androstanediol
20α-Dihydrotrengestone
16α-Hydroxyestrone
5α-Dihydroethisterone
8,9-Dehydroestrone
8,9-Dehydroestradiol