What are Bioidentical Hormones?

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  • Written By: Karyn Maier
  • Edited By: Bronwyn Harris
  • Last Modified Date: 19 January 2020
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Bioidentical hormones are plant-derived hormones that are promoted as an alternative to conventional hormone replacement therapy (HRT) for menopausal women. As the name implies, they are alleged to be identical to hormones produced in human females in terms of molecular structure. However, even though bioidentical hormones are obtained from plants, they do not occur naturally. Instead, they are synthesized from chemical agents found in soy and yams.

Specifically, the bioidentical hormones are 17 beta-estradiol, estrone, and estriol, the form of estrogen that declines as a woman ages. Since there is no bioidentical version of progesterone, it is simply micronized and added to the preparation to ensure better absorption. Some formulations are sold as over-the-counter products. They are also compounded, meaning that they are custom blended by a pharmacist in accordance with a physician’s prescription.

As might be expected, the availability of bioidentical hormone replacement therapy (BHRT) versus prescription-based HRT drugs has triggered a good deal of public interest, as well as controversy. Certainly, concerns have been raised about the safety of HRT drugs, some of which contain conjugated equine estrogens derived from the urine of pregnant horses. In fact, the sale of these drugs has fallen off considerably since two major studies revealed that they increase the risk of heart attack, stroke, and breast cancer. Not surprisingly, sales of “natural” bioidentical hormones were bolstered as a result.


In a backlash maneuver, the manufacturers of one of the most popular HRT drugs petitioned the U.S. Food and Drug Administration (FDA) to limit the availability of compounded bioidentical hormones, but without success. However, the FDA had already taken notice of unsubstantiated claims being touted by certain pharmacies that BHRT compounds could help prevent stroke, certain cancers, and Alzheimer’s disease. While the FDA took action against the use of these misleading claims, they did not prohibit the sale of bioidentical hormones. It’s also interesting to note that the term bioidentical has no regulatory definition, meaning that it has become an advertising word much like “natural” or “eco-friendly.”

In terms of actual safety, there is no solid evidence to indicate that bioidentical hormones are any safer than FDA-approved HRT drugs. In fact, some physicians believe that they may pose just as much risk as their equally synthetic counterparts. There is also the consideration that individually compounded formulas cannot be compared to any standard protocols with which to measure safety and efficacy. Finally, there is a school of thought that asserts hormonal replacement therapy of any kind involves certain risks and should only be administered in the short-term to reduce severe menopausal symptoms.

Until more clinical trials on bioidentical hormones have been completed, a middle-of-the-road approach may be most appropriate. That said, there are several FDA-approved bioidentical estrogen and progesterone formulas available in various doses and forms that don’t require inconsistent compounding.


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