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)
Estriol is an estrogen, or an agonist of the estrogen receptors, ERα and ERβ. It has been found to possess 11–14% and 18–21% of the relative binding affinities of estradiol for the human ERα and ERβ, respectively, while its relative transactivational capacities at these receptors were 11% and 17%, respectively. In addition to being a ligand of the classical nuclear ERs, estriol is an antagonist of the GPER, a membrane estrogen receptor, at high concentrations. This is in contrast to estradiol, which is an agonist of this receptor. Like other estrogens, estriol does not importantly interact with other steroid hormone receptors.