17 OH, steroid

Estrogen may also refer to any substance, natural or synthetic, that mimics the effects of the natural hormone. The steroid 17b-estradiol is the most potent and prevalent endogenous estrogen, although several metabolites of estradiol also have estrogenic hormonal activity. Synthetic estrogens are used as pa of some oral contraceptives, in estrogen replacement therapy for postmenopausal women, and in hormone replacement therapy for trans women.Ref: Ganong&;s review of medical physiology; 24th edition; page no:- 409