Overview — Estrogen

The hormone estrogen, produced in a woman's ovaries and adrenal glands, travels via the blood to target areas throughout the body. In the breasts and elsewhere in the reproductive system, estrogen acts as a growth hormone.

Within each breast are 10-12 milk ducts that branch into lobules. Lobules are composed of milk glands. The cells lining the milk glands contain estrogen receptors. Estrogen binds to the receptors and triggers cell growth, preparing the breast to produce milk if a woman should become
pregnant.

Estrogen also acts upon other areas of the body, reducing cholesterol levels in the heart and liver and preserving bone strength.