Estrogen is produced in the ovaries and the production of estrogen is controlled by 2 hormones. There are secondary sources of production of estrogen such as the liver, breasts and adrenal glands but this secondary production is very small as compared to the ovaries.

There are three principle forms of estrogen found in the human body estrone, estradiol and estriol. Estradiol production is most commonly thought of as an endocrine product of the ovary; however, there are many tissues that have the capacity to synthesize estrogens from androgen and to use estrogen in a paracrine or intracrine fashion. In addition, other organs such as the adipose tissue can contribute significantly to the circulating pool of estrogens.

Estradiol is the most commonly measured type of estrogen for nonpregnant women. The amount of estradiol in the blood varies throughout her menstrual cycle. After menopause, estradiol production drops to a very low but constant level. However, after menopause or a hysterectomy, estrogen production decreases by about 40% to 60%. In other words the female body still produces estrogen at about 40% to 60% of pre-menopause levels.
more
http://www.isoflavones.info/estrogen.php
http://www.health-science.com/menopause.html
http://www.ncbi.nlm.nih.gov/pubmed/11511861


The primary sources of Estrogen Production include the corpus lectum, placenta and ovary. The development of follicles in these parts of the body lead to Estrogen Production. Thus the development of follicles have a direct relation with the production of Estrogen. The amount of Estrogen Production from these parts of the body are the maximum. Thus in a woman capable of reproduction, the primary source of estrogen are the main source fro the hormone. In ovaries, luteinizing hormone or LT and follicle stimulating hormone or FSH act as stimulants in Estrogen Production.


The secondary sources of Estrogen Production includes some tissues in the body. These tissues include liver, breasts as well as adrenal glands. For the women who have crossed the menopausal stage these kind of secondary sources of the hormone is very important. They do not have adequate estrogen from the primary source of the hormone so the secorndary sources becoem more importat for them.
more
http://www.pregnancyxl.com/pregnancy/pregnancy-hormones/estrogen/production.html

Another major change that occurs after menopause is that estrogen production shifts from the ovaries to the fat cells in a woman's body. The chief estrogen of postmenopause is estrone (E1) which is converted from androgens (i.e., androstenedione) produced mainly by the adrenal glands. Some estrogen continues to be produced by the adrenals but in a lesser amount. The ovaries have now begun to shrink in size, although they never disappear and, in fact, they still have quite an important role in postmenopause since some hormones (ie. testosterone) continue to be produced there.
more
http://womens-health.health-cares.net/postmenopause.php

The synthesis and secretion of estrogens is stimulated by follicle-stimulating hormone (FSH), which is, in turn, controlled by the hypothalamic gonadotropin releasing hormone (GnRH).
High levels of estrogens suppress the release of GnRH providing a negative-feedback control of hormone levels.
more
http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/S/SexHormones.htmlfeedback control of hormone levels.