The female menstrual cycle is largely controlled by the hormones estrogen and progesterone. Estrogen causes the lining of the uterus, the endometrium, to thicken each month, to be ready to implant an embryo. Progesterone causes the lining to be shed each month if no embryo implants. When large amounts of estrogen are present with little or no progesterone, the endometrium continues to thicken without being shed. This condition is known as estrogen dominance or unopposed estrogen, and it can increase the risk endometrial cancer as well as other health problems.
Causes of Estrogen Dominance
The proper method for preventing estrogen dominance depends upon what is causing the estrogen dominance. Estrogen dominance can result from something that causes higher levels of estrogen, something that causes lower levels of progesterone or something that causes a combination of the two. The most common causes of excess estrogen are obesity and hormone replacement therapy (HRT), although there are uncommon tumors that can lead to overproduction of estrogen as well. The most common cause of decreased progesterone is anovulation, or failure to ovulate, which is usually caused by polycystic ovary syndrome, or PCOS.
Hormone Replacement Therapy
Post-menopausal women normally have extremely low levels of both estrogen and progesterone. The lack of estrogen is responsible for the increased risk of osteoporosis as well as the mood symptoms many women experience during menopause, and HRT is commonly used to help with these problems. Early approaches to HRT used only estrogen, but as the dangers of unopposed estrogen have become more apparent, combined estrogen/progesterone regimens have become more common. Combined therapy has risks of its own, however, as can be seen from an article published in the January 2008 issue of the journal Cancer Epidemiology, Biomarkers & Prevention, which found that post-menopausal women using estrogen and progesterone for three or more years experienced an increased risk of a certain type of breast cancer.
Obesity
Obesity is the most common reason for increased estrogen in pre-menopausal women and a significant source of unopposed estrogen after menopause as well. Fat cells convert other hormones to estrogen, and an increased number of fat cells results in increased estrogen. Obese women have an increased risk of endometrial cancer, endometriosis and uterine fibroids, probably as a result of their higher levels of estrogen, according to information published in the textbook "Williams Gynecology." Obesity is also associated with increased insulin resistance, and insulin resistance plays a major role in PCOS.
Polycystic Ovary Syndrome
The name "polycystic ovary syndrome" is a bit misleading, since the ovarian cysts often found in the syndrome are a symptom, rather than a cause, of the disorder. Cysts may form whenever a woman does not ovulate normally, although they do not necessarily do so. While there are many possible causes of anovulation, PCOS is by far the most common. The symptoms of PCOS include increased body hair and irregular or unusually long or heavy periods. While the full details of how PCOS develops are uncertain, it is clear that insulin resistance plays a major role. Obesity is a major contributor to PCOS through its effect on insulin resistance. In addition, the constant production of excess estrogen from fat cells may interfere with the normal cyclical levels of estrogen that are essential to a normal ovulatory cycle. So obesity is both a cause of excess estrogen and, if it leads to PCOS, decreased progesterone.
Preventing Estrogen Dominance
The best way for most women to prevent estrogen dominance is by maintaining a healthy weight. In addition, exercise, even without significant weight loss, can reduce insulin resistance and decrease the chances of developing PCOS, according to recommendations in "Williams Gynecology." If a woman does have symptoms of PCOS, she should see a doctor for definitive diagnosis and treatment. Oral contraceptives are usually an effective treatment for PCOS in women who do not wish to become pregnant. For women who do want to get pregnant, monthly use of the drug Clomid can induce ovulation in many cases. The diabetes drug metformin is also useful, both by itself and in concert with Clomid, although it has gastrointestinal side effects that some patients find difficult to tolerate. HRT in post-menopausal women remains controversial. There is no single best course of treatment, since the decision to use opposed versus unopposed estrogen or any HRT at all depends upon balancing several different risks with the perceived benefits. The patient's family history and personal preferences play a major role in finding the correct balance.
References
- "Williams Gynecology"; John O. Schorge; 2008
- Cancer Epidemiology, Biomarkers & Prevention; Relationship between Menopausal Hormone Therapy and Risk of Ductal, Lobular, and Ductal-Lobular Breast Carcinomas; Christopher Li; January 2008
