“Bioidentical” hormones have often been promoted in the popular press as safer and more effective than FDA-approved hormones. However, there’s no good evidence to support this assertion. This is just one of several claims about bioidentical hormones therapy that Harvard Women’s Health Watch examines in its September 2011 issue.

The term bioidentical doesn’t have an exact medical definition. Health experts generally define bioidentical hormones as compounds that have the same chemical and molecular structure as those produced in the body. Some bioidentical hormones, like natural progesterone (Prometrium) and estradiol products such as Estrace, Vivelle, and Estring are FDA-approved and available by prescription. “Bioidentical” is more broadly defined by advocates of “bioidentical hormone replacement therapy” (BHRT), which includes hormone testing via saliva tests and the use of individually compounded hormones to correct “deficiencies.” It’s the claims made for BHRT that Harvard Women’s Health Watch calls into question. These include:

BHRT hormones are not drugs but are molecular copies of natural hormones – This is not true. Drugs are substances (other than food) that are intended to affect the structure or any function of the body. If custom-compounded hormones have effects in the body, they’re drugs.

Bioidenticals are safer than synthetic hormones – This is unknown. Compounded hormones haven’t been tested at all in clinical trials, and even FDA-approved bioidentical hormones haven’t been tested in large, long-term trials like the Women’s Health Initiative (which tested synthetic hormones).

Estriol (a weak estrogen used in compounded hormones) offers women protection from breast cancer – There is no evidence that this is true.

Saliva and blood tests are reliable indicators of hormone levels – This is not true. Such tests can only tell a woman’s hormone level at one moment in time and thus are not useful for setting hormone doses. In menstruating and perimenopausal women, hormone levels change from hour to hour. In postmenopausal women, there’s no “normal” level of these hormones or levels that correlate with symptoms.

Read the full-length article: "Bioidentical hormones: Help or hype?"