A womans uterus is designed to deal with normal estrogen by way of her monthly period, which sheds estrogen stimulated cells. With menopause, her body decreases it is production of estrogen because her estrogen-producing egg follicles are all gone.
When a woman is exposed to too much estrogen, it creates a situation called estrogen dominance, which causes a whole host of problems. With estrogen dominance, cells stop dying (which is what cells are supposed to do as they age and become abnormal) and continue to divide uncontrollably. This can eventually lead to cancer.
Aside from cancer, estrogen dominance has other problems. Its related to mid-life obesity, PMS, recurrent breast pain, endometriosis, fibroids, rheumatoid arthritis, and lupus. For men, excess estrogen is now widely considered the likely culprit in prostate disease.
Estrogen dominance is caused by several factors. Age and obesity are the most common. As we age and gain weight, an unwanted enzyme found in fatty tissue called aromatase becomes more prevalent in our body. This enzyme captures precious testosterone, already in decline with age, and spits it back out as estrogen. That is why you are hearing a lot about aromatase-inhibitor drugs in estrogen-related breast cancer. Inhibiting the enzyme reduces testosterone conversion to estrogen. The best way to keep that enzyme in check is to keep lean and get plenty of exercise!
Another cause of estrogen dominance is genetics. Each of us has genetic factors that contribute to the development of estrogen-related cancers. In part, these factors are greatly magnified by your exposure to xenobiotics.
Xenobiotics are man-made poisons. They are everywhere in our environment, including the food chain. They include chlorinated hydrocarbons and pesticides, which can have powerful estrogen-like effects on your body that are far stronger than your natural estrogens.
Regardless of where the estrogen comes from, your body has to get rid it. To do so, the liver has to go through a biochemical process called hydroxylation. When the liver hydroxylates estrogen, it creates various types of estrogen byproducts.
There are many of these estrogen byproducts (rather than naming all of them, we typically refer to them by their hydroxyl position in the estrogen chain). Some are dangerous and some are beneficial. For instance, scientists and doctors typically pay attention to two of them: the 2 and 16 positions (a.k.a. 2-hydroxy estrogen and 16-hydroxy estrogen). The 2-hydroxy estrogen is considered beneficial. It works to cause normal cell death (called apoptosis), which prevents cancer.
On the other hand, 16-hydroxy estrogen causes cancer and inflammation. (Just remember that 2 is good and 16 is bad.)
Many labs measure the ratio of 2-hydroxy to 16- hydroxy estrogens to help assess your disease risk. A good ratio is 2:1. If the ratio is lower, you are at greater risk of cancer and any number of inflammatory diseases.