What Exactly Are Bio (Body) Identical Hormones?
I recently received a great DM on instagram asking me to explain what bio (body) identical hormones are and how they are different from what is the birth control pill or what was looked at in the Women’s Health Initiative study.
Bio or body identical are hormone preparations such as estradiol (an estrogen) or progesterone that look exactly like the hormones you have in your body. These are commercially available at your local pharmacy such as the popular estradiol patches or Prometrium (the progesterone pill). Estradiol and progesterone can also be compounded at compounding pharmacies. Progesterone cream is often available over-the-counter as well that is bio (body) identical. Of note, yam cream is not progesterone cream UNLESS the ingredients actually list USP Progesterone.
There are other non-bioidentical options such as ethinyl estradiol (which is in the combination birth control pill), conjugated equine estrogen (such as Premarin), and various forms of synthetic progestins. A progestin is not the same as progesterone but it can bind to progesterone receptors. They can also act rather androgenic depending on the generation of the medication. Medroxyprogesterone acetate (MPA) is Provera. Both Premarin and Provera were used in the controversial hormone study, The Women’s Health Initiative (WHI), over 20 years ago. They are often referred to as “synthetic” forms of hormones as they are NOT bio or body identical. They are not identical to what is in your body.
Quick note - despite the words ‘estradiol’ used in ethinyl estradiol or ‘progesterone’ used in medroxyprogesterone acetate - they are NOT bio (or body) identical. They should not be used interchangeably either. If you’re looking for actual estradiol, make sure what you’re getting is plain estradiol! Same goes for progesterone.
The WHI study results came out in 2002 with the headline grabbing headlines that hormones caused breast cancer (and a number of other things). This caused a huge percentage of women to stop their hormone therapy or be pulled off their hormone therapy. Many years later, we know this study was full of flaws, including their own interpretation of the results.
It turns out, even the Washington Post did a recent article discussing a JAMA article calling the fears “overblown.” The combination of conjugated equine estrogen (Premarin) coupled with medroxyprogesterone acetate (Provera) did have a slight increase in breast cancer.
How much increased risk of breast cancer? The UK’s NICE reports 0.8 cases per 100 women using combination synthetic therapy.
The estrogen only group did not. Unfortunately, that part never made the news until MUCH later and everyone still thinks estrogen single handedly causes cancer.
Right now given all the options available, the current literature (and my personal preference) leans much more towards bio (body identical) estradiol coupled with actual progesterone (Seo, Baye, McDonald 2022) as the best option. Thankfully as I said, this can be readily available at your every day pharmacy or compounded if you’re not able to tolerate the typical commercial routes or doses.
Last quick note, there is another form of estrogen known as estriol. You might have this for vaginal dryness or in a combination estrogen cream known as bi-est. Estriol is a bio (body) identical form of estrogen as well. It is available at compounding pharmacies.
Citations:
Seo Hyon Baik, Baye F, McDonald CJ. Effects of Hormone Therapy on survival, cancer, cardiovascular and dementia risks in 7 million menopausal women over age 65: a retrospective observational study. medRxiv (Cold Spring Harbor Laboratory). Published online May 26, 2022. doi:https://doi.org/10.1101/2022.05.25.22275595