Stop Using “Body Identical” and “Bioidentical” to Refer to Menopausal Hormone Therapy

They are predatory marketing terms, not medicine

“Body identical” and its sister term “bioidentical” are being used more and more by medical professionals and this is problematic, because not only are these terms incorrect and medically meaningless, they are often used to imply that certain form of menopausal hormone therapy, or MHT, are “natural” and thus inherently safer. 

Let’s unpack this because it is important to understand what is marketing and what is science and I think you will learn a fair bit about hormones as well. 

What are the Main Reproductive Hormones Made By the Body?

Before menopause, the two estrogens produced by the ovary are estradiol and estrone. They are also produced in other tissues, such as muscle, fat, and the brain. Before menopause, estrogen levels in the blood are much higher because there must be sufficient amounts to travel through the blood to stimulate the lining of the uterus, as well as other tissues. With menopause, the production of both estradiol and estrone drops significantly as the main source in the blood is from the developing follicle. Levels of estrone don’t drop as much, because a significant amount of estrone is produced in other tissues.

The other hormone in MHT is a progestogen. This means either progesterone, which is made by the corpus luteum, the tissue left after ovulation, or a progestin, which is semi-synthetic hormone that acts like progesterone on may tissues. A good analogy is to think of progesterone as cow’s milk and progestins as soy milk. Similar in many ways and both called milk, but also some key differences. Progestins, for example, are better at controlling irregular bleeding than progesterone, and progesterone can help with sleep, whereas progestins don’t.

“Body identical” or “Bioidentical” typically means estradiol, estrone, and progesterone.

“Body identical” and “Bioidentical” Imply they are Natural, which is a Marketing Ploy. 

The point of using the terms “body identical” and “bioidentical” seems to be to imply they are natural, and hence safe, because they are the “same” (more on that in a bit) as what the body made before menopause. So you are just replacing “what is “lost.” This is an odd tactic and deceptive as the body isn’t supposed to make estrogen in high levels after menopause, so giving estrogen in MHT is decidedly unnatural. See, you can twist the language of “natural” to mean what you want! But doesn’t that sound more palatable to say you are “replacing what was lost” as opposed to the more accurate statement, “MHT is a pharmaceutical intervention that can help many women. There are some small risks, and so women should decide based on the evidence if MHT is right for them.” 

In addition, I find this idea that MHT is replacing what was “lost” patriarchal and ageist. Women do not become  “less” due to  menopause. And, to be more precise, women do not “lose” estrogen with menopause, they simply stop producing it. This is a planned end. The end of ovarian function is no more a loss than becoming an adult is the loss of childhood, medically speaking. The fact that there are symptoms in menopause that trouble some women doesn’t mean you should have estrogen, no more than having morning sickness in pregnancy means that being pregnant is unnatural or that you shouldn’t be pregnant. It means medicine should find a solution.

The terminology of “bioidentical” originated with people who have zero understanding of menopause or reproductive physiology. It can be traced to the so-called functional medicine movement in the early 80s that used the slogan, “Horse estrogen is for horses.” This was long before the Women’s Health Initiative (WHI) was published. It was popularized by anti-vaccine “natural” medicine people, like the odious and ignorant Dr. Christiane Northrup. (You can read more about her here). There was no data at the time supporting the safety of estradiol over the common alternative at the time, conjugated equine estrogens (Premarin). Ironically, Premarin, which is extracted unchanged from horse urine, is in fact the only truly natural medicine for MHT, as all others require synthesis.

As “bioidentical” has been adopted largely by those prescribing compounded and less safe hormone preparation, the equally incorrect “body identical” appears to have sprung up to refer to pharmaceutical preparation of estradiol and progesterone.

So Called “Bioidentical” and “Body Identical” Estrogens Are Not Safer Because They are Similar to the Estrogens Made by The Ovary.

The estrogen that your body makes can cause cancer, this is well proven with endometrial cancer. In addition, the estrogen and progesterone made by the body has a role in breast cancers for some women. Even the small amounts of estrogen produced in tissues, like muscle, can have a negative effect after menopause for women with hormone receptor positive breast cancer. That is why these women are treated with medications to block the small amounts of estrogen produced in these tissues.

Being the same or similar as made by your body does not mean a hormone is safe. However, terms like “body identical” and “bioidentical” are used to imply safety, because what the body makes is safe, right? Wrong. I can give someone pharmaceutical estradiol, which is similar but never identical to what the body makes, and give them cancer of the uterus. It just takes enough estrogen and enough time. This is the sole reason we give progesterone or a progestin, a progesterone-like medication with estrogen, to prevent the cancer of the uterus that estrogen can cause.

Being found in nature or being similar to what the body makes are not the reasons something is safe or should be used.  For example, there is ongoing work with estetrol, an estrogen made by the fetal liver. Using, or rather abusing, the term natural it would be decidedly unnatural to take an estrogen for menopause that is only made by the fetal liver, and yet if it is proven to be safe and effective it would be an excellent option. 

Which Hormones Are The Safest?

What we do know is progesterone may have a slightly lower rate of breast cancer when used in MHT compared to progestins, and so oral progesterone is recommended as the first line therapy for women who need a progestogen (a progesterone or a progestin) to protect their uterus. Progesterone is not safer because the pharmaceutical we give is similar to what the body makes, it is safer because that is what the studies show. That took me just 74 words to explain in the first two sentences in this paragraph, no marketing terms needed. 

As for the safety of estradiol over conjugated equine estrogens? Again, this has nothing to do with the made up concept of “natural” or being “bioidentical.” Transdermal estradiol, meaning a patch, a pharmaceutical lotion or spray, or a vaginal ring called Femring (where the hormone is absorbed into the body, so not the same as vaginal therapy), are all safer than conjugated equine estrogens (Premarin), likely because they are transdermal. Conjugated equine estrogens are only available orally (the vaginal cream is for the vagina only). When estrogen is taken orally it increases the risks of blood clots, likely due to the way it is metabolized in the liver into estrone, which interestingly appears to be more likely to induce clots. 

That took 93 words to explain. 

See, you can explain the safest hormones and why without resorting to marketing terms. 

So Called “Body identical” and “Bioidentical” Hormones are Not Natural, They are Made In a Lab by Semi Synthesis

To be natural, a medication must be found in nature and the chemical structure must remain unaltered. Think boiling salt water and you are left with the salt. So if estradiol were extracted from ground up human ovaries it would be natural. Fortunately, that is not how it is made today. As an aside, powdered extracts of cow ovaries were used over a hundred years ago. That would be a natural therapy. Apparently the taste was awful.

As mentioned, the only natural estrogen is conjugated equine estrogens (Premarin), which are extracted from horse urine. Pharmaceutical estradiol and progesterone are made in a lab by a process called the Marker degradation. A chemical is extracted from yams or soybeans, and this starting chemical is not an estrogen or even a steroid. This chemical is then exposed to multiple chemicals over multiple steps to chemically convert this non-estrogen into an estradiol or progesterone. This process is known as semi-synthesis. 

Being natural or being made by semi-synthesis doesn’t make something safe, being studied appropriately is how we know something safe and how we identify risks. I know, I sound like a broken record. 

So called “body identical” or “bioidentical” hormones ARE NOT EVEN IDENTICAL TO WHAT THE BODY MAKES

Yes, I am shouting, because this is so infuriating. Do medical professionals who call estrogens and progesterone “identical” not understand how they are made? Well, I do, so let me explain.

Identical means exactly that. The same at a molecular level. But a hormone made in the lab by the Marker Degradation cannot be identical to a hormone made by the ovary. 

All chemical elements have isotopes, which are variations with different numbers of neutrons. Carbon, the element that forms the backbone of steroid hormones, like estradiol and progesterone, has two naturally occurring isotopes, known as 12C and 13C. Hormones made in the lab all come from a single source, the chemical extracted from yams or soybeans. So these semi-synthetic hormones all have one 12C/13C ratio. However, the body makes estradiol and progesterone from cholesterol, as we get our cholesterol from a variety of plant and animal sources, each with its own 12C/13C ratio. So the estradiol and progesterone made by the human body will have hormones with varying 12C/13C ratios and those made in a lab will have a fixed 12C/13C ratio. A good analogy for this is bags of halloween candy, one that is only peanut butter cups (to represent the hormones made in a lab) and the other consisting of a variety pack, with peanut butter cups, Hershey bars, Snickers, and Almond Joy. While these are both bags of candy, they are not identical.

As far as your body is concerned, the 12C/13C ratio doesn’t matter, so either bag of candy in our analogy will do, but it is inaccurate to call estradiol made in the lab identical to the estradiol made by the body. You can call estradiol or progesterone made in a lab biosimilar or body similar, but not bioidentical or body identical.

So What Does This Mean?

Using terms like “bioidentical” and “body identical” falsely implies that hormones in MHT are “natural” and hence “safe” and possibly even something that every woman “needs”, as opposed to what MHT really is, an excellent therapy for hot flushes, sleep disturbance related to hot flushes, a therapy that can help prevent osteoporosis, and something that can help with mild depression in the menopause transition. MHT can also help with bleeding irregularities in the menopause transition.

When given vaginally, estrogen is an excellent treatment for vaginal changes of menopause, but when we discuss MHT we mean hormones that enter the bloodstream, which is not the case with vaginal therapy.

I suspect some practitioners use these terms “bioidentical” or “body identical” to imply they are offering something more “natural” or safer. Perhaps if your entire practice is selling hormones, you need to build them up as much as possible? And I suspect some practitioners just find these terms easier to use, which is sad because that shows how much marketing has contaminated MHT

I trust women can learn and understand the differences between the hormones that are prescribed for MHT, which is why I won’t use the terms “body identical” or “bioidentical”. 

Selected References

Yen & Jaffe’s Reproductive Endocrinology, 8th Edition. Strauss and Barbieri. Elsevier 2019.

Reame, NK. Estetrol for menopause symptoms: The Cinderella of estrogens or just another fairy tale? Menopause 2020;27.

Bagot CN, Marsh MS, Whitehead M, et al. The effect of estrone on thrombin generation may explain the different thrombogenic risk between oral and transdermal hormone replacement therapy. Journal of Thrombosis and Hemostasis, 2010. 

Stute P, Wildt L, Neulen J. The Impact of micronized progesterone on breast cancer risk: A systematic review. Climacteric 2018;21.

The Menopause Manifesto. Dr. Jen Gunter 2021 Kensington Publishing Corp.

Bhavnani BR, Stancyk FZ. Misconception and concerns about bioidentical hormones used for custom-compounded hormone therapy. Journal of Clinical Endocrinology and Metabolism 2012;97.