Bioidentical Hormone Replacement Therapy

The term “bioidentical” is a bit misleading because many think that it indicates entirely natural human hormones.

Bioidentical hormones are chemically identical to human hormones but they are synthesized from natural (plant) sources. They can be produced in pre-set dosages and if made by a pharmaceutical company, are regulated by the Food and Drug Administration (the FDA). Bioidentical hormones can also be compounded by a pharmacist to match the precise dose as written by your physician. Those bioidentical hormones specifically made on the orders of the physician are an example of individualized medicine, with the recognition that just as “one size does not fit all” one dosage does not fit all.

There are those that suggest that compounding pharmacies are not regulated by the FDA as the drug companies are and that increases the risk of low quality product and of greater variability from one batch to the next. It is technically true that the FDA does not regulate compounding pharmacies, so the best approach appears to be to work with a compounding pharmacy with an excellent reputation. It is also important to work with a physician that has experience using bioidentical hormones with that specific compounding pharmacy—in other words, your physician and your compounding pharmacy should have a solid professional relationship.

Some Basic Facts about Bioidentical Hormones  1, 2, 3

  • Always remember that whether you are taking conventional HRT or are working with a compounding pharmacy, the goal is always to use the least amount of hormone for the shortest time possible. While bioidentical hormones have been used very safely in Europe for decades, that doesn’t mean they are entirely risk free. The endocrine (hormone) system is incredibly complex and we are trying to “tweak” a normal and natural transition in order to relieve specific symptoms. But, it IS a complex system and a cautious approach is warranted.
  • The bioidentical estrogens can contain three different forms of estrogen: 17 beta-estradiol, estrone, and estriol. The 17-beta-estradiol is the form of estrogen that decreases the most during peri-menopause. The bioidentical progesterone is most often synthesized from compounds found in soy and yams. It is usually dried and then ground to a very fine powder (micronized) in order to increase its absorption into your body.
  • Another thing to remember about bioidentical hormones is that they can come in essentially the same forms as the conjugated estrogens and progestins (the synthetic analogs of human estrogens and progesterone). Estrace, for example, is 17 beta-estradiol in a pill form while Estring is 17 beta-estradiol in a vaginal ring form. Similarly, Prometrium is a micronized bioidentical progesterone that comes as a pill and Prochieve (4%) is a micronized bioidentical progesterone that comes as a vaginal gel.
  • Most bioidentical estrogens are prescribed with 2 forms of estrogen (Bi-est) or with all three forms of estrogen (Tri-est). Bi-est contains 20% estradiol and 80% estriol Tri-est usually combines the estrogens in a 10%:10%:80% (estrone:estradiol: estriol) ratio which approximates the natural ratio of these forms of estrogen. Another advantage is that the more powerful estradiol (and potentially the more problematic) is at a lower level with the estriol serving as a precursor or forerunner of the estradiol. These estrogens should be balanced with progesterone—the exact amount of progesterone used will depend on a number of factors.
  • Before you embark on any HRT, most physicians experienced with bioidentical HRT will test your levels of the three estrogens and progesterone. This can be done by testing either your blood or your saliva and can help determine the starting levels of the estrogens and the progesterone. 4
  • During your HRT your physician will likely be following up every 3-6 months with testing and assessment of your symptom relief. Always tell your healthcare practitioner if your symptoms get worse or if you experience irregular vaginal bleeding, especially if you are post-menopausal.
  • You should also be aware that some manufacturer’s label their product “bioidentical” but they are more like “biologically-really-similar-and-almost-identical” Talk to your compounding pharmacist to make sure that they are using truly bioidentical hormones.
  • Many practitioners prefer non-oral delivery systems—more simply put, many practitioners believe that giving both estrogens and progesterone through the skin (as a patch, gel or cream) is the most effective and most “natural” approach. Estrogens and progesterone that is delivered via the skin bypass something called “first-pass metabolism” by the liver—and this essentially means that more hormone gets to more tissues without being altered by normal liver reactions.
  • Most menopause specialists will try to achieve a normal “physiologic” level of the hormones—anti-aging specialists, on the other hand, tend to believe that higher levels of hormones can limit the effects of aging. What all this really comes down to is what you are trying to achieve—if you are trying to achieve symptom relief, again, the lowest dose possible for the shortest time possible is the maxim you should observe. The anti-aging properties of hormones are not very well tested—after all, we all age and our hormones do seem to decrease with age. I prefer dietary and lifestyle approaches to anti-aging, myself.


  1. Conaway E. Bioidentical hormones: an evidence-based review for primary care providers. The Journal Of The American Osteopathic Association 2011;111:153-64.
  2. Holtorf K. The bioidentical hormone debate: are bioidentical hormones (estradiol, estriol, and progesterone) safer or more efficacious than commonly used synthetic versions in hormone replacement therapy? Postgraduate Medicine 2009;121:73-85.
  3. Korownyk C, Allan GM, McCormack J. Bioidentical hormone micronized progesterone. Canadian Family Physician 2012;58:755-.
  4. Marsden T. Bioidentical Hormone Replacement: Guiding Principles for Practice. NatMedJ 2010;2.

Speak Your Mind