It been shown to be very effective for these problems, but the list of possible side effects includes possibility of birth defects, breast cancer, blood clots, fluid retention, acne, rashes, weight gain, and depression. The side effects of Premarin and Provera may be the main reason why hormone replacement therapy is causing so much confusion among the women of America. In humans, estrogen has three different forms, one of which, estriol, has been shown to be safe and effective in studies to date. Estriol is used extensively in Europe for estrogen replacement therapy in menopausal and postmenopausal women, but it has rarely been used for that purpose in the U.S. Evidence suggests that estriol offers many of the benefits of more traditional estrogen-replacement therapies, but without the harsh side effects or longer term dangers often encountered by other trademarked products. During pregnancy, huge amounts of estriol are secreted by the placenta to protect the fetus.
Doctors measure the urine estriol to determine the condition of the fetus.
Estriol, in studies so far, seems to be protective for cancer and endometrial hyperplasia. This ratio of estrogens is how they are produced in the female human body. Natural progesterone, as opposed to the synthetic progestins, seems to be protective against breast cancer. It has been shown to increase bone mass in osteoporosis. It improves menopausal symptoms and depressed feelings.