Types & Formulations of Bioidentical Estrogens
Compounded estrogen formulations for menopause contain estradiol, estrone and/or estriol.[5,16,17] Currently, products such as Biest (biestrogen) containing 20% estradiol and 80% estriol, and Triest (triestrogen) containing 10% estradiol, 10% estrone and 80% estriol, expressed on a mg per mg basis, are prepared by compounding pharmacies for patients. It appears that Biest, available as capsules, sublingual compounds and transdermal cream or gel is clearly the most common preparation used.[5,16,17] It is important to understand that although the percentage of estrogens defines the compound, pharmacies vary in the total mg dose of Biest they dispense. For example, one pharmacy may prepare a 1.25 mg preparation of Biest (which contains 0.25 mg estradiol with 1.0 mg estriol), while another prepares a 2.5 mg preparation of Biest (which contains 0.5 mg estradiol and 2.0 mg estriol).[16] Thus, the total weight in mg of the preparation dispensed by a particular pharmacy is the most important factor in understanding the doses of estrogens used by patients. In an informal telephone survey of four local US compounding pharmacies and three large national compounding pharmacies in Colorado, Texas and Wisconsin, identified through the internet, the 2.5 mg dose of Biest is the common transdermal estrogen preparation recognized by all seven compounding pharmacies at the time of writing.
The potency of estriol ranges from 1/10 to 1/100 that of estradiol, with 1/80 most often cited,[18] leading one to believe that any benefits of Biest for menopausal symptoms may be more related to the estradiol component rather than to the estriol component. Estriol as the sole estrogen in any preparation is not commercially available in the USA, but is available commercially in Europe, mostly as vaginal preparations. Some practitioners in Europe may not consider vaginal estriol to be a bioidentical hormone, despite the fact that it has a structure like endogenous estriol. In a randomized, placebo-controlled trial of 88 women, 2 mg estriol alone as a daily dose vaginally in the absence of estradiol was reported to have beneficial effects on urogenital outcomes, including vaginal dryness, dysparunia, urogenital atrophy and in urodynamic testing variables, including maximum urethral pressure, mean maximum urethral closure and abdominal pressure transmission ratio.[19] This study of estriol demonstrates that it may have beneficial effects as a single hormone for urogenital symptoms.
Women's Health. 2008;4(2):163-171. © 2008 Future Medicine Ltd.
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