Women going through menopause, the period of life when the menstrual cycle ends, produce the reproductive hormone estrogen at much lower levels than during their fertile period. Because the decline in estrogen and other reproductive hormones causes changes in the body, some women choose to take estrogen supplements to alleviate the symptoms associated with menopause. Unfortunately, traditional estrogen supplements are synthetic, processed in a laboratory from substances foreign to the human body, and are associated with a number of dangerous side effects, notably breast cancer. Natural estrogen replacement therapy is a newer option that many women and physicians consider to be safer and gentler on the body. It is important to note that menopause is a natural stage of life, not an illness, and not every woman requires hormone replacement therapy during menopause.
The most commonly prescribed form of estrogen replacement is conjugated equine estrogen, which is synthesized from pregnant mare's urine. It has been in use since the 1950s. In addition to the three forms of estrogen naturally occurring in the human body -- estradiol, estrone, and estriol -- conjugated equine estrogen also contains equilin, an estrogen molecule specific to horses whose effects on the human body is unknown. Possible side effects of conjugated equine estrogen include heart attack, stroke, breast cancer, and deep vein thrombosis.
Natural estrogen, also called bioidentical estrogen, has recently appeared as an alternative to conjugated equine estrogen, and other synthetic formulas. It contains only the naturally occurring human estrogen molecules estradiol, estrone, and estriol. While synthetic estrogen supplements are most often taken orally, natural estrogen is more often administered through transdermal patch or as a cream. Many proponents of natural estrogen replacement therapy believe that many of the side effects associated with traditional hormone replacement therapy may be due to taking the supplements orally. Oral estrogens also carry a higher risk of blood clotting than transdermal estrogens.
While some studies have suggested that natural estrogen does not carry the same risks as conjugated equine estrogen, such as blood clots, natural estrogen is a relatively new technology, and there is less information available from studies. The largest problem with natural estrogen supplements is that they are not currently regulated by the United States Food and Drug Administration (FDA). Many of the claims pharmacists make about their natural estrogen products are unsubstantiated. Natural estradiol and progesterone, another reproductive hormone often used in hormone replacement therapy, are both available in FDA-approved products, however.