To function optimally, the female body requires an optimal balance of estrogens (a trio of related hormones called estradiol, estrone, and estriol) and progesterone. Estrogen dominance occurs when the hormonal balance is shifted in favor of the estrogens. This condition just as correctly could be called progesterone deficiency.
How does this happen? For the most part, it is the inevitable result of the aging process. A woman’s ovaries generally function best between a few years after puberty until around age thirty. However, as a woman ages, so do her ovaries. By the time a woman reaches thirty-five years of age she is over halfway through her menstrual life and her ovarian function begins to falter.
Each of the ovaries contains numerous follicles, which hold a woman’s eggs.
At ovulation, a mature (vesicular) follicle ruptures, releasing its egg. The follicle is then transformed into a progesterone-producing corpus luteum. If ovulation does not occur, no corpus luteum forms, and no progesterone is made.
The ovaries are the primary site for the production of both the estrogens and progesterone. But while both estrogen and progesterone levels decline with age, progesterone declines much more dramatically. By menopause, a woman’s progesterone level is likely to be a mere 1/120 of the level she experienced in her early twenties. In contrast, her postmenopausal estrogen level may remain at 40 percent of the level she experienced in early adulthood, because even when her ovaries no longer produce estrogen, her fat cells continue to do so. Thanks to this additional source of estrogen, an obese postmenopausal woman may have higher estrogen levels than a thin premenopausal woman.
Another reason why estrogen dominance becomes more common with age is that as a woman ages she begins to have anovulatory cycles, menstrual cycles during which her ovaries do not release eggs. When a woman does not ovulate, her ovaries produce no progesterone at all. The stimulatory effects of estrogen unopposed by progesterone can cause the endometrial lining to become abnormally thickened, resulting in heavier periods, clotting, and painful menstrual cramps. As women enter their thirties, anovulatory cycles become more common, and symptoms of estrogen dominance become progressively more severe.
Other Causes of Estrogen Dominance
While estrogen dominance is usually a progressive condition that develops as women move through their menstrual lives, it is virtually inevitable after a hysterectomy. As with natural menopause, surgically induced menopause obliterates progesterone production—immediately, rather than over years. Even if the ovaries have been spared the surgeon’s knife, ovarian dysfunction or atrophy commonly occurs within two years following removal of the uterus, causing a predictable decline in progesterone levels.
Bilateral tubal ligation also can lead to a decline in the production of hormones by the ovaries. This procedure, in which the fallopian tubes are cut, burned, or tied off to prevent pregnancy, cuts off a portion of the blood supply to the ovaries. Many women who have undergone this procedure develop bilateral tubal ligation syndrome with symptoms of estrogen dominance.
Estrogen dominance can also occur following childbirth. During pregnancy, the placenta produces progesterone at levels that are many times higher than a woman’s body normally produces. When the baby is delivered and the placenta is expelled, there is a precipitous drop in the progesterone level. However, estrogen levels remain high. Unless the ovaries can produce adequate amounts of progesterone to balance the estrogens, estrogen dominance is likely to occur.
Another factor contributing to estrogen dominance is the presence of xenoestrogens in our bodies. Xenoestrogens are found in petrochemical products such as plastics, herbicides, pesticides, soaps, clothing, industrial by-products, and countless other manufactured goods. The prefix “xeno” means alien, an apt description of these synthetic chemicals, which pollute the water, air, soil, and animal and plant life on this planet. Xenoestrogens can cause estrogenic effects even in doses on the level of a billionth of a gram, and because they are stored in the fat cells of our bodies, most of us carry a significant burden of these toxic chemicals.
Oral contraceptives are another common cause of estrogen dominance, because they work by suppressing ovulation and ovarian function. Keep in mind that a woman who is not ovulating produces no progesterone in her ovaries. Oral contraceptives contain progestins, not progesterone. Like xenoestrogens, synthetic progestins are alien to a woman’s body, and although they target the same cell receptors that progesterone targets, their effects do not perfectly mimic those of the natural hormone. In fact, they depress the body’s production of natural progesterone, leading to estrogen dominance and its associated symptoms.