stating that manufacturers of estriol would have to create a new application and estriol would be treated as a new drug. Its use is not approved by Health Canada; estriol is not available as a pharmaceutical preparation in Canada or the United States, but is a commonly prescribed conventional treatment in other countries and is available as a cream or vaginal suppository in the United Kingdom and the European Union. Estradiol is available as brand-name products in both oral and transdermal forms. Progesterone Progesterone is used both orally and transdermally. Oral progesterone is micronized (ground) to increase availability and is approved by the FDA to treat endometrial hyperplasia when used in opposition to estrogen. It has also been approved to relieve menopausal symptoms, either alone or in combination with estrogen. It is more reliable in treating menopausal sleep disorders than synthetic progestins. Transdermal progesterone is often used as a component of compounded BHT but has not been clinically proven to prevent endometrial hyperplasia, as oral progesterone has. The editors-in-chief of the scientific journal Climacteric state that the greatest difference in function between bioidentical and synthetic hormones may be found in progesterone's behavior compared with progestin. Laboratory studies have suggested that bioidentical progesterone binds primarily to progesterone receptors, while synthetic progestins activate other receptors with a variety of effects. The editors suggested that progesterone may have neutral to positive effects on the cardiovascular system, and induce apoptosis in breast epithelial cells. These compounds have not been directly compared with each other in appropriate scientific tests, though as of 2010 trials had begun. Progesterone is approved for use by both the FDA and Health Canada as a brand-name oral preparation. The French epidemiological study "Etude Epidemiologique aupres de femmes de l'Education Nationale" suggested micronized progesterone may offer a reduced risk of breast cancer compared to other progestins, though large-scale clinical trials have not been conducted. A 2012 practice advisory published by Canadian Family Physician concluded "there is no convincing evidence that bioidentical hormones are safer or more effective than synthetic HRT". Other hormones Testosterone supplementation can improve libido in postmenopausal women, but can also reduce levels of high-density lipoproteins. Commercial sources for testosterone for women in the United States are limited and include the estrogen-testosterone mixture Estratest; compounding pharmacies are the main source of testosterone-only preparations for women. A testosterone patch has been approved for use in the United Kingdom and European