What are Bio-identical Hormones?

Many women perceive that plant estrogens (or phytoestrogens), because they are “natural,” are safer than standard FDA approved estrogens. Data on phytoestrogens for the relief of hot flashes are conflicting, but the majority of studies have not demonstrated benefit.

 The “bio-identical” approach generally refers to the prescribing of individualized doses of steroid hormones (compounded as pills, gels, sublingual tablets, or suppositories). Many women assume that “natural” hormones are safer; but what does safer mean?

Bioidentical hormones are identical in molecular structure to the hormones women make in their bodies. They are synthesized from a plant chemical extracted from yams and soy. The bioidentical estrogens are 17-beta-estradiol, estrone, and estriol. The quality of compounded products may be substandard in some cases. In one study, potencies ranged from 67.5% to 268% of the amount specified on the labeling. The hormones most commonly compounded are estradiol, estrone, estriol, progesterone, testosterone, and dehydroepiandrosterone (DHEA). Women typically are asked to submit saliva or blood samples to measure baseline hormone concentrations. Based upon the results, the prescriber selects the individual hormones and doses to be compounded. This approach can be expensive. Most experts say these tests are of little value because there is no evidence that hormone levels in saliva correlate with response to treatment in postmenopausal women.

Advocates of the bio-identical hormones claim that these hormones are effective for menopausal symptoms yet are safer and better tolerated than commercially available hormones. However, a review of the literature concluded that, while some of these products may decrease hot flushes, there is no evidence that “bio-identical” hormones have any advantage over conventional hormone therapies. The US Food and Drug Administration (FDA) has published consumer information warning consumers that many claims made about the safety and efficacy of compounded bio-identical hormone products are false and misleading, with no credible scientific evidence to support them. In a 2006 position statement that was reissued in 2009, the Endocrine Society stated that there is no scientific evidence to support the efficacy, safety, or effectiveness of compounded bio-identical hormones.