<unk> (E1), sold under the brand names Estragyn, Kestrin, and Theelin among many others, is an<unk> n medication and naturally occurring steroid hormone which has been used in menopausal hormone therapy and for other indications. It has been provided as an aqueous suspension or oil solution given by injection into muscle and as a vaginal cream applied inside of the vagina. It can also be taken by mouth as estradiol/estrone/estriol (brand name Hormonin) and in the form of prodrugs like estropipate<unk> sulfate; brand name Ogen) and conjugated<unk> ns (mostly<unk> sulfate; brand name Premarin). Side effects of<unk> ns like<unk> include breast tenderness, breast enlargement, headache, nausea, fluid retention, and edema, among others.<unk> is a naturally occurring and bioidentical<unk> n, or an agonist of the<unk> n receptor, the biological target of<unk> ns like endogenous estradiol. It is a relatively weak<unk> n, with much lower activity than estradiol. However,<unk> is converted in the body into estradiol, which provides most or all of its<unk> nic potency. As such,<unk> is a prodrug of estradiol.<unk> was first discovered in 1929, and was introduced for medical use shortly thereafter. Although it has been used clinically in the past,<unk> has largely been discontinued and is mostly no longer marketed.
Estrone 
Methyltestosterone
Allyltestosterone
Androgen
Estradiol
Estradiol 
Dihydrotestosterone
2-Hydroxyestradiol