Estrone sulfate is a sulfated estrone derivative. Estrone sulfate acts as a long-lived reservoir that can be converted as needed to the more active estradiol (from estrone via 17 beta-hydroxysteroid dehydrogenase). Estrone Sulfate (E1S) is the most abundant circulating estrogen in non-pregnant women as well as normal men. Estrone is primarily synthesized from estrone sulfate. Estrone is an estrogenic hormone secreted by the ovaries and adipose tissues. Estrone is one of the three estrogens found in humans. The other two are estriol and estradiol. Estrone is the least prevalent of the three. Estradiol plays a critical role on reproductive and sexual functioning in women and it also affects other organs including the bones. Estriol is an estrogen that is prevalent primarily during pregnancy. [HMDB]