No, bioidentical hormones do not cause cancer. This false impression began in 1991, when the very controversial Women’s Health Initiative (WHI) was halted due to increased incidence of chronic disease among subjects. This study used the synthetic hormone, Prempro, and subjects of the study were and average age of 63 years. Meta-analyses following this study, including some as recent as November 2011, have shown that most of the subjects had pre-existing conditions that lead to the development of disease during the study and that hormones actually reduce the risk of cancer and other chronic diseases in women.
In fact, more than 15 major medical organizations now endorse hormone therapy as a safe and effective treatment plan for many adverse health conditions.