Estrone is one of the three main estrogens produced by the human body. Estrone (also oestrone) is an estrogenic hormone secreted by the ovary. Estrone is the least prevalent of the three hormones, estradiol being prevalent almost always in a female body, estriol being prevalent primarily during pregnancy.

Estrogens (also oestrogens) are a group of steroid compounds, named for their importance in the oestrus cycle, functioning as the primary female sex hormone. While estrogens are present in both men and women, they are usually present at significantly higher levels in women of reproductive age. They promote the development of female secondary sex characteristics, such as breasts, and are also involved in the thickening of the endometrium and other aspects of regulating the menstrual cycle. Follicle stimulating hormone (FSH) and luteinizing hormone (LH) regulate the production of estrogen in ovulating women. Since estrogen circulating in the blood can feedback to reduce circulating levels of FSH and LH, some oral contraceptives contain estrogens.

Formal Chemical Name (IUPAC)
(8R,9S,13S,14S)-3-hydroxy-13-methyl-7,8,9,11,12,13,15,16-octahydro-6H-cyclopenta[a]phenanthren-17(14H)-one

References

http://en.wikipedia.org/wiki/Oestrogen