Hormone therapy is very tightly regulated when it comes to standard prescriptions therapy that women are used to, but it is also possible to have your gyno write a dosage and formulation that is specifically mixed for you. Most all these mixed products are made from plants such as the yam or soy. This is what is known as bioidentical and also compounded therapy. Compound therapies may be necessary for a very few women, and these formulas have undergone a very small amount of research. Since studies with compounded therapies have been very small, and very short in duration , there is no long term safety data, and some women have been led to believe that the lack of data is proof of the increased safety of these medications. ACOG in 2012 came out against the compounded bioidentical hormone prescriptions and now the Endocrine Society has come out against this position as well. The Aug 2012 position paper on bioidenticals from the American College of Obstetricians and Gynecologists reads much like the position papers that this and other gyno organizations have put out before. They conclude that the evidence to propound that these compounds are safer than traditionally prescribed FDA approved medications is lacking. They go on to say that the compounded products have more variability in the dosing and formulation so they may in fact be less safe. Estriol is a placental estrogen that is actually fairly weak. Estriol probably has a bit less harmful effect on bone, it is uncertain it's effects on the breast, and it has about the same negative
effects as estradiol on the uterus. Estriol cannot be found in any traditional pharmaceutical products, but has to be obtained in a compounded formulation. Formulas called Tri-est usually combine estriol, estradiol, and estrone into a prescription, and Bi-est is formulated from estriol and estradiol. The percentages of these two compounds in these formulas do not mimic "natural" levels in the woman, they are still pharmacological dosages. Natural hormone levels in a menopausal woman are quite low.
In the ACOG position paper they remind patients and their gynos to treat these medicines like any other hormone prescription in terms of monitoring and safety. They also conclude that testing of levels: urinary, salivary, or blood for management of the individualized dosing is not proven effective either. In conclusion, they support conventional therapy over compounded bioidentical therapy. For women who are not relieved by their hormone therapy, it is a good idea to gab with your gyno about alternatives, including these alternatives.