Bioidentical hormones, a marketing term not recognized by the US Food and Drug Administration (FDA), refers to exogenous hormones biochemically similar to those produced within the body and includes 17A-estradiol (predominant estrogen before menopause), estrone (predominant estrogen after menopause), estriol (from placenta), progesterone (ovaries, placenta, and adrenal glands), testosterone (ovaries and adrenal glands), and their conjugates. These are derived from soy and yam precursors and must be chemically processed to make them able to be absorbed by the human body.
Hormones that meet the definition of bioidentical are available as FDA-approved prescription therapies and include estradiol (oral, patch, gel, lotion, mist, and vaginal ring, cream, or tablet) and micronized progesterone (oral or vaginal). The FDA has not approved estriol. Custom-compounded bioidentical hormone products are prepared, assembled, and packaged according to a provider's prescription into gels, creams, lotions, sublingual tablets, subdermal implants, suppositories, or troches. Transdermal therapies avoid the first-pass effect through the liver, and there is evidence that they have a lower clotting risk. Progesterone may have fewer negative effects than synthetic progestins on lipids, sleep and mood, and breast (density, tenderness, and cancer risk) when combined with estrogen. No FDA-approved testosterone therapy (bioidentical or otherwise) is available for women.
Lack of Testing for Efficacy, Safety, and Quality Control
The major difference between FDA-approved hormone products meeting the definition of bioidentical versus custom-compounded products is that the former are regulated by FDA, tested for purity, potency, and efficacy, and sold with FDA-approved product information that includes boxed warnings. Efficacy and safety data, required for obtaining particular product indications, have been demonstrated in randomized, clinical trials with peer-reviewed published reports for FDA-approved bioidenticals but not for custom-compounded products.[4,5]
No large, long-term studies have been done to determine the effectiveness, safety, or adverse effects of custom-compounded bioidentical hormones. In 2008, because of lack of scientific data on estriol, FDA stated that pharmacies should not compound drugs containing estriol unless the prescriber has a valid investigational new drug application.