Furthermore, there is no proof that bioidentical hormones
from so called "natural" sources or that have been "custom compounded" are safer than or even as effective as traditional HRT. The fact that the FDA (the governmental Food and Drug Administration) does not monitor or regulate the production of biodidentical hormones is another primary concern of health care providers.
Now concrete evidence that justifies years' worth of warnings has been published: an article in the Medical Journal of Australia describes three separate cases of postmenopausal women (54, 59, and 71 years of age, respectively) using bioidentical hormones who were subsequently diagnosed with endometrial cancer.
Eden, Hacker, and Fortune, the authors of this study, proposed a variety of potential dangers associated with bioidentical hormones. First of all, the compounding of bioidentical hormones is not regulated by any governing body, and the administration routes (like tablets, lozenges, or creams administered to the skin) have not been tested for efficacy.
The researchers propose that the most important factor, however, may be the practice of compounding the bioidentical hormones based on the results of salivary hormonal tests, which are not accurate indicators of hormonal levels. Due to this, the compounders may fail to add adequate levels of progesterone to the compound, which is essential to protect against the cancer-stimulating effects of estrogen alone. Alternatively, the administration routes may facilitate for the absorption of only estrogen, while progesterone was less completely absorbed.
The authors of this study as well as the Australian Menopausal Society and North American health organizations like the North American Menopause Society formally discourage the use of bioidentical hormones until further studies have been conducted. Women who continue to use bioidentical hormones despite the warnings are encouraged to be regularly screened for endometriosis and cancer in order to catch any possibly developing disease in their early stages.