In 2002, the Women's Health Initiative reported an increased risk between hormone replacement therapy and breast cancer. The study showed that out of 10,000 women taking estrogen plus progestin hormone replacement therapy, 41 would develop breast cancer, as opposed to only 33 women per year out of 10,000 in the placebo group. Furthermore, those who developed breast cancer while taking the estrogen plus progestin hormone replacement therapy were found to have larger tumors that were more invasive. While this study did alert the public's attention to the increased risk between hormone therapy and breast cancer, it didn't define the risk of other hormone therapies, such as growth hormone therapy, estrogen only therapy or bioidentical hormone replacement therapy.
Growth hormone therapy is often used to promote growth children who are deficient in naturally occurring growth hormone, including those afflicted by chronic renal insufficiency, Prader-Willi syndrome, and Turner syndrome. However, in recent years, growth hormone therapy has also been used to promote growth in children who simply seem shorter than average, and has also been used in some anti-aging regimens in adults.
Since the release of the Women's Health Initiative study, it has come to light that growth hormone therapy also increases one's risk of developing breast cancer. Although growth hormone therapy doesn't contain the same hormones as estrogen and progestin therapy, it still seems to affect breast cancer cells by increasing the production of insulin-like growth factor (IGF-1). In testing, IGF-1 has been shown to cause breast cancer cells to multiply more rapidly than normal, even more than estrogen. So, while growth hormone therapy may be appropriate for those who truly need it, for those seeking an anti-aging remedy, the risk of breast cancer would seem to outweigh any potential (and unproven) benefits.
While growth hormone therapy may be less common in the general population, there are plenty of women who use an estrogen patch as hormone replacement therapy. The Women's Health Initiative actually did do a study on women using estrogen only, but the results remained much less quiet than those of the estrogen plus progestin study. The study of women using solely estrogen showed no increased risk of breast cancer. So for those women who are successfully using an estrogen patch, there is really no cause for concern when it comes to breast cancer.
Finally, many women who undergo hormone replacement therapy choose to avoid synthetic hormones and instead favor bioidentical hormone replacement therapy. The proponents of bioidentical hormones claim that because the hormones are derived from plant sources and the hormones are identical to those produced naturally in the body, there is no increased risk of breast cancer. However, it is important to note that bioidentical hormones are not FDA approved and there have been no clinical trials on them. Therefore, the American College of Obstetricians and Gynecologists recommends that bioidentical hormone replacement therapy be treated as though it held the same risks as tradition hormone replacement therapy.
So far, research has shown that both estrogen plus progestin hormone therapy and growth hormone therapy puts users at an increased risk for breast cancer. This does not mean, however, that they are not useful therapies for some patients. The bottom line is that you should discuss all of your concerns with your doctor and make an educated, informed decision before starting any hormone therapy.