What Is Progesterone? Why Your Body Needs It
Progesterone is a hormone your body naturally makes. It balances estrogen, supports fertility and pregnancy, protects bone and breast health, calms the brain and nervous system, and helps with sleep.
But here’s the problem: when researchers tried to make progesterone into a pill back in the 1940s and 50s, it was rapidly broken down by the liver. That meant oral doses weren’t reliable and well absorbed, and natural progesterone couldn’t be turned into a convenient, profitable drug.
The Creation of Medroxyprogesterone: A Profitable Substitute
Pharmaceutical companies solved this “problem” in the 1950s by chemically tweaking the progesterone molecule. By adding an acetate group at the 17-alpha position, they created a new drug: medroxyprogesterone acetate (MPA).
This made the compound:
- Patentable (unlike natural progesterone, which can’t be owned).
- Stable and orally active (it wouldn’t break down as quickly).
- Marketable as a brand-new product (Provera for hormone therapy, Depo-Provera for contraception).
Medroxyprogesterone wasn’t just about solving a medical challenge. It was about creating a profitable, patent-protected drug.
Progesterone vs. Progestins: Understanding the Key Differences
This is where things get confusing. In medical literature, all compounds that bind to progesterone receptors, including natural progesterone and synthetics like medroxyprogesterone, were lumped into one category: progestins.
But biologically, they are not the same.
- Natural Progesterone (bioidentical): Identical to what your body makes. It binds only to progesterone receptors, supporting sleep, mood, breast protection, bone health, and cardiovascular balance.
- Synthetic Progestins (like medroxyprogesterone): Chemically altered. While they activate progesterone receptors, they also bind to androgen and glucocorticoid receptors. This creates off-target effects that progesterone does not have. And you don’t get theh benefits related to sleep, anxiety, mood and bone health
Why Doctors Call Progestins “Progesterone” (and Why It’s Misleading)
Medical training still uses “progestin” and “progesterone” almost interchangeably. That means your doctor may say you’re being prescribed “progesterone” when you’re actually getting Provera (a synthetic progestin) or other synthetic progestin like norethindrone (a birth control pill). ALL birth control pills contain synthetics as do IUDs and MHT combo patches.
This shorthand creates real-world confusion. Many women assume they’re taking the same hormone their body naturally makes, when in reality they’re taking a drug with very different effects and very different risks.
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The Health Risks of Medroxyprogesterone Compared to Progesterone
Research has consistently shown differences in outcomes between bioidentical progesterone and synthetic progestins:
- Medroxyprogesterone has been linked to increased risk of breast cancer.
- Bioidentical progesterone shows a safer profile. Studies suggest it is breast-protective and supportive for bone health.
What the Women’s Health Initiative Revealed About Synthetic Progestins
The Women’s Health Initiative (WHI) trial in the early 2000s tested hormone therapy using conjugated equine estrogen (Premarin) plus medroxyprogesterone (Provera). The results? Higher risks of breast cancer, blood clots, and heart disease.
The increased risk of heart attacks and strokes is largely due to the way oral estrogen is metabolized, not due to medroxyprogesterone. However, the breast cancer risk was attributed to synthetic progestin on sub analysis of the study and has been shown in subsequent studies of IUDs and birth control pills.
Millions of women stopped hormone therapy overnight, and fear around MHT still lingers today.
But here’s the nuance: the risks were tied to synthetic progestins like medroxyprogesterone—not to bioidentical progesterone, which was not studied. Unfortunately, because the WHI didn’t study bioidentical hormones, the distinction was lost in headlines and medical training.
Follow the Money: How Profit Shaped Women’s Hormone Therapy
So why did medroxyprogesterone and conjugated equine estrogen become the standard in the first place?
- Patents. Natural progesterone and estradiol couldn’t be patented, but medroxyprogesterone could.
- Marketing. With patent protection, companies could invest heavily in promotion.
This story isn’t just about biology. It’s about business shaping medical practice—and women paying the price.
What Women Should Ask Before Starting Hormone Therapy
If you’re considering hormone therapy, here are some questions to ask:
- Am I being prescribed natural progesterone or a synthetic progestin?
- What are the known risks of this drug, and how do they compare to bioidentical progesterone?
- Are my hormones being tested to personalize my therapy?
- Is my provider experienced with customizing bioidentical hormone therapy, or are they relying on one-size-fits-all protocols?
The Bottom Line: Protecting Your Health with the Right Hormone Choices
Medroxyprogesterone was created to solve a business problem as much as a medical one. While it offered convenience, it also carried risks that natural progesterone doesn’t.
And decades later, because of how doctors are trained to lump everything into the “progestin” category, women are still left confused and underserved.
You deserve to know the difference. Because when it comes to your hormones, healthspan, and longevity the details matter.
References
- Writing Group for the Women’s Health Initiative Investigators. JAMA. 2002;288(3):321-333.
- Fournier A, et al. J Clin Oncol. 2008;26(8):1260-1268.
- Stute P, Wildt L, Neulen J. Climacteric. 2018;21(2):111-122.
- Prior JC. Climacteric. 2018;21(4):366-374.
Dr. Anna Garrett is a menopause expert and Doctor of Pharmacy. She helps women who are struggling with symptoms of perimenopause and menopause find natural hormone balancing solutions so they can rock their mojo through midlife and beyond. Dr. Anna is the author of Perimenopause: The Savvy Sister’s Guide to Hormone Harmony. Order your copy at www.perimenopausebook.com.
Dr. Anna is available for 1-1 consultation. Find out more at www.drannagarrett.com/lets-talk
