Bioidenticals: Signifying Nothing

Sandra Adamson Fryhofer, MD


September 04, 2012

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Hello, I'm Dr. Sandra Fryhofer. Welcome to Medicine Matters; the topic, hormone replacement therapy and the truth about bioidenticals. A new review in the Cleveland Clinic Journal of Medicine clears up common misconceptions and sets the record straight.[1] Here's why it matters.

In 2002, the Women's Health Initiative dramatically changed medicine's views on the safety of hormone replacement therapy (HRT).[2] After that, discussions on HRT expanded from the doctor's office to self-help books, talk shows, and celebrities with product endorsements.

We now have a different lingo for talking about hormones. The new buzz term is "bioidentical," but what does that really mean?

The term indicates that the molecular structure of the drug is identical to the endogenous hormones estrogen, progesterone, and testosterone. Three estrogens circulate in the human body:

  • 17-beta estradiol, the most biologically active;

  • estrone, a derivative of estradiol and the second most dominant estrogen; and

  • estriol, a very short-acting estrogen and the least biologically active.

The first misconception is that US Food and Drug Administration (FDA)-regulated drugs are not bioidentical. This is wrong. A long list of FDA-approved hormone products contain 17-beta estradiol and, therefore, are bioidentical. Examples include oral esterase, estradiol transdermal patches (Climara®, Vivelle®) and the vaginal ring (Estring®). Prometrium® is an oral FDA-approved bioidentical progesterone product.

The next misconception is that progesterone-containing skin creams protect the endometrium. This is false; these creams are not strong enough. In addition, some creams contain an inactive progesterone precursor that the human body can't metabolize.

Many topical forms of progesterone -- gels, lotions, creams -- are made at compounding pharmacies. Some can be purchased over the counter at health food stores. Such progesterone creams are not strong enough to raise blood levels sufficiently to protect the endometrium from estrogen stimulation. Transdermal progesterones therefore do not protect against endometrial cancer in patients taking estrogen.

Another misconception is that compounded therapy is safer. That just isn't so. Compounded therapy may be marketed as being safer, but these claims are false and misleading. Because these products are not FDA-approved, there are no guarantee as to their purity, potency, and efficacy. There is also no proof that compounded products are more effective or that they have fewer side effects. They also often aren't covered by insurance and therefore may cost more.

The final misconception regards saliva hormone testing. It's a gimmick. Although the concept of making a hormone combination just for you sounds appealing, the FDA says that saliva hormone testing has no scientific basis, and it's not reliable.

These are just some key points from this study. For more details, read the entire review.[1] For Medicine Matters, I'm Dr. Sandra Fryhofer.