What is a Bioidentical Hormone?
Hormones are called bioidentical or natural if they are exact duplicates of what your body makes. The molecular structure of a bioidentical hormone is identical to that of the hormones made by your body. This is an important distinction because the hormones often prescribed by doctors are not bioidentical; in fact many are not found anywhere in nature. These are called synthetic hormones.

Bioidentical vs. Synthetic Hormones—What's the Difference?
One of the best examples of a synthetic hormone is the commonly prescribed menopause drug PremPro. This stands for Premarin and Provera. Premarin is an estrogen made from the urine of pregnant mares. Provera is a synthetic progesterone, known as a progestin. Provera has been shown to increase a woman’s risk of heart disease, stroke and breast cancer. This is in contrast to bioidentical progesterone, without which a woman cannot get pregnant or stay pregnant. The fetus is bathed in progesterone during the third trimester of pregnancy. Bioidentical progesterone is very safe! Synthetic progestins are not safe!

Why are Bioidentical Hormones Safer than Synthetic Hormones?
Hormones do very complex and specific jobs in the body by fitting into parts of your cells called receptors, much the same way that a key fits into a lock. Once the hormone is in the receptor, it gives the cell instructions. If the molecular structure of the hormone is different, the instructions given to the cell are different. Bioidentical hormone instructions have evolved within the human body for thousands of years, so your body knows how to use them, and how to safely dispose of them. Synthetic hormones that aren’t natural to your body often give instructions that are harmful.
For example, a progestin may give the cells some of the same instructions as bioidentical progesterone, but it may also give other instructions, and it will often send a much stronger message.

How Do I Know Whether I’m Using a Bioidentical or Synthetic Hormone?
Bioidentical human estrogens are called estradiol, estrone and estriol. The most common estrogen used in hormone replacement is estradiol.
Bioidentical progesterone is simply called by its own name—progesterone.
Bioidentical testosterone is also simply called by its own name—testosterone.

Are the Hormones in My Birth Control Pills Bioidentical or Synthetic?
All of the hormones found in chemical birth control are synthetic. There are no bioidentical hormones in birth control pills.

Where Can I Find More Detailed Information about Bioidentical Hormones?
If you want a great education about bioidentical hormones, the best book you can read is What Your Doctor May Not Tell You about Menopause.
If you’re looking for a broader overview, read Hormone Balance Made Simple.

More Information about Bioidentical Hormones
Estrogen Advice from Dr. John Lee
Bioidentical Estrogen—How Much to Take and When
Bioidentical Hormones and Heart Disease
Bioidentical Hormones and Breast Cancer