How is estrogen produced?

Estrogen is produced in the ovaries, primarily the theca (wall) of developing follicles in the ovary, though also to a lesser extent the corpus luteum (remaining outer 'shell' which previously contained an egg) and, during certain stages of pregnancy, the placenta.

Some estrogens are produced in smaller quantities by liver, adrenal glands and the breasts.These secondary sources of estrogens are especially important in postmenopausal women. Fat cells produce estrogen as well.