Estrogen is the major sex steroid hormone produced by ovaries in women. However, estrogen is also produced in a lesser amount in men. There are receptors for estrogen in many other cells of the body of men and women including the brain, bones, and blood vessels.
Because women have more estrogen than men and less cardiovascular disease than men of the same age up to about 50 years old (menopause), estrogen is considered to protect the vasculature against disease processes. Estrogen stimulates release of nitric oxide from endothelial cells and decreases division and contraction of smooth muscle cells. Whether or not estrogen treatment to women after menopause protects against development of atherosclerosis is controversial. The time past menopause at which treatment is initiated may be important. This idea is being tested in a clinical trial called KEEPS (Kronos Early Estrogen Prevention Study; Climacteric 2005;8:3-12).
In addition, the type and dose of estrogen alone or in combination with other hormones like progestins influences the magnitude and type of changes in endothelial cells. Experiments in our laboratory investigate how different types of estrogens (17β-estradiol, estrone sulfate, conjugated equine estrogen (also known and Premarin®) and synthetic estrogen-like compounds used in the treatment of cancer (tamoxifen and raloxifene) affect endothelial cells and platelets.