Estrogen

(CC) Image: David E. Volk
Estrogen steroids, suchas as estrone and estradiol, are produced from androgens such as androstenedione and testosterone.

An estrogen is a type of steroid hormone with eighteen carbons. With increasing age and menopause, the levels of estrogens decrease in women, and estrogen replacement therapy has been used for decades to decrease the systoms associated with menopause. However, recent studies suggest that estrogen replacement therapy increases the risks of heart attacks and strokes, so its use is now declining. The steroids estrone and estradiol are both estrogens.

Biosynthesis

The estrogens are biosynthesized, by several chemical modifications of androgens. The C-3 ketone group is reduced to an alcohol, the C-19 methyl group is removed and the "A" ring (see steroid for numbering and nomenclature) becomes an aromatic ring.