Bio-identical hormones may be either from a natural source or synthetically made, and it’s more about the molecule being identical to the human molecule that our body normally makes, than whether it comes from a natural source.
With the exception of Premarin, which is extracted from the urine of pregnant mares, virtually all replacement and contraceptive hormones, in all forms, bio-identical or synthetic, are first extracted from soybeans or wild yams in a laboratory. Those that are processed so that they exactly match the molecular structure of the hormones made by the human body have come to be called bio-identical, to distinguish them from synthetic hormones, which have a molecular structure that is not found in nature, and certainly not in the human body.
The bio-identical hormones typically used for hormone replacement include progesterone, estradiol, estriol and testosterone. If they are called medroxyprogesterone acetate, or methyltestosterone for example, they are synthetic and are best avoided if you want to stay healthy.
If you baked a cake and then extracted only the wheat flour from it in a laboratory, there would be no more cake—it would just be wheat flour. Similarly, once the hormone is extracted from the soybean or wild yam, there is no more wild yam or soybean in it, so it really makes no difference where it originally came from, as long as the molecular structure is identical.
Synthetic hormones are made by adding chemical groups that will make the hormones not-found-in-nature so they can be patented and you can pay a lot of money for them. Unfortunately your body really doesn’t know what to do with these freaky tweaked molecules and they all have undesirable side effects.
What Is Natural?
So, there is no such thing as a “natural” or “synthetic” bio-identical hormone. All bio-identical hormones are made in a laboratory and shipped off by the barrel to be made into pills, patches, gels, creams, troches, suppositories and injections. The estradiol found in a patch or pill made by a giant pharmaceutical company likely came from the same factory as the estradiol made into a cream in a compounding pharmacy. If the hormones you’re taking are estradiol, estriol, progesterone or testosterone, then you’re taking a bio-identical hormone regardless of who makes them, sells them, or what form they’re in.
Fortunately most of the synthetic estrogens in oral contraceptives have been phased out and replaced with ethinyl estradiol, which is almost bioidentical—the ethinyl part of the molecule is quickly knocked off in the gut so by the time it gets to the bloodstream it’s just estradiol.
The synthetic hormones that menopausal women really need to avoid are the synthetic progesterones, called progestins, such as medroxyprogesterone acetate (e.g. Provera), norethindrone acetate (e.g. Activella) and levonorgestrel (e.g. Climara).
For more detailed information about these differences Hormone Balance Made Simple by Dr. John Lee and Virginia Hopkins is an excellent guide.