<unk>  is an<unk> rane steroid. It is also known as 17β-estradiol (to distinguish it from 17α-estradiol) or as<unk> ra-1,3,5(10)-triene-3,17β-diol. It has two hydroxyl groups, one at the C3 position and the other at the 17β position, as well as three double bonds in the A ring. Due to its two hydroxyl groups,<unk>  is often abbreviated as<unk> . The structurally related<unk> rogens,<unk> rone (E1),<unk> riol (E3), and<unk> etrol (E4) have one, three, and four hydroxyl groups, respectively.
Estradiol
Estrogen
Estrogen 
Alfatradiol
Androgen
Progesterone 
Progesterone
Methyltestosterone