Estradiol sulfate
As the sodium salt, sodium estradiol sulfate, E2S is present as a minor constituent (0.9%) of conjugated equine estrogens (CEEs), or Premarin. It effectively functions as a prodrug to estradiol in this preparation, similarly to E1S. E2S is also formed as a metabolite of estradiol, as well as of estrone and E1S. Aside from its presence in CEEs, E2S is not available as a commercial pharmaceutical drug.
Estriol (medication)
Estetrol (E4), also known as 15α-hydroxyestriol, is a naturally occurring analogue of estriol with an additional hydroxyl group, at the C15α position. It is closely related to estriol and has similar but non-identical pharmacological properties. Like estriol, estetrol is a relatively weak and atypical estrogen. Estetrol is under development for potential clinical use for a variety of indications, such as menopausal hormone therapy and hormonal birth control.https://adisinsight.springer.com/drugs/800034634