When bio-identical hormones are dosed correctly to compensate for the individual's hormone deficiency, they are safe. While there are no large studies regarding the safety of bio-identical hormones over synthetic hormones, providers and pharmacists alike view bio-identical as a better alternative when hormone replacement is indicated.
As with every medication or supplement, the potential side effects of use versus the consequences of treatment refusal (in this case meaning continued hormone deficiency and associated risks) must be weighed. Use of estrogen (synthetic and bio-identical) is contraindicated for women with cancer. For any woman taking estrogen, it is important to balance it with progesterone, which offers some protection against breast cancer. Studies do show that Progesterone (bio-identical) reduces the risk of breast cancer while progestin (synthetic) increases the risk of breast cancer.
If you are considering BHRT (bio-identical hormone replacement therapy), we recommend that you review your personal risk factors for breast cancer (take the risk assessment test at www.cancer.gov/bcrisktool) and determine if the small increase in risk with the use of estrogens is worth the benefits.