Bioidentical hormones are made from plant compounds extracted from wild yams and soybeans. The key starting ingredient is diosgenin, a plant steroid found in the roots of wild yam species (from the Dioscorea family). Through a series of chemical reactions in a laboratory, diosgenin is converted into hormones that are structurally identical to the ones your body produces naturally, including estrogen, progesterone, testosterone, DHEA, and cortisol.
The “bio” in bioidentical refers to this molecular match. These hormones aren’t simply ground-up yam root. They’re pharmaceutical products synthesized through precise chemistry, and the final molecule is indistinguishable from what your ovaries, testes, or adrenal glands make on their own.
The Plant Source: Wild Yams and Soy
There are over 600 species of wild yam, and several contain diosgenin in their roots. The connection between yams and hormone production dates back to the 1940s, when chemist Russell Marker discovered he could extract diosgenin from a Mexican wild yam species called cabeza de negro and transform it into progesterone. Soybeans contain similar plant steroids and serve as an alternative starting material for the same conversion process.
One common misconception is that eating wild yam or applying wild yam cream can raise your hormone levels. It can’t. Your body has no way to convert diosgenin into estrogen, progesterone, or any other hormone on its own. That conversion requires laboratory chemistry. Supplements marketed as “natural progesterone from wild yam” without actual synthesized progesterone on the label won’t have hormonal effects.
How Plant Steroids Become Human Hormones
The laboratory process that turns diosgenin into progesterone is called the Marker Degradation, named after Russell Marker, who invented it. It works because part of the diosgenin molecule already resembles human steroid hormones. The reactive portion of the molecule’s side chain, where two oxygen atoms connect to the same carbon atom, can be chemically stripped away. What remains mirrors the side chain of progesterone.
In practical terms, the process starts with extracting yam roots using alcohol, then evaporating the liquid down to a concentrated syrup. That syrup undergoes the Marker Degradation reaction sequence, which removes the unwanted parts of the molecule. Additional chemical modifications to the steroid ring structure yield progesterone itself. From progesterone, chemists can further modify the molecule to produce estradiol, testosterone, and other hormones.
The finished product is chemically identical to the hormone your body makes. As the pharmaceutical labeling for USP-grade progesterone states, it “is synthesized from a starting material from a plant source and is chemically identical to progesterone of human ovarian origin.”
How They Differ From Non-Bioidentical Hormones
Not all hormone medications are bioidentical. The most well-known example is Premarin, a brand of conjugated estrogens isolated from pregnant mare urine (the name is literally short for “pregnant mares’ urine”). First reported in 1938, it contains a mixture of estrogens found in horses, some of which don’t occur naturally in humans. It works, but its molecular structure doesn’t match human estradiol.
Synthetic progestins like medroxyprogesterone acetate (the active ingredient in Provera) are another example. These are lab-made molecules designed to mimic progesterone’s effects, but their chemical structure has been deliberately altered from the human version, often to improve oral absorption or extend duration. Bioidentical progesterone, by contrast, uses the exact same molecule your body produces, typically in a micronized (finely ground) form to help with absorption.
FDA-Approved vs. Compounded Forms
Bioidentical hormones come in two very different categories, and the distinction matters for quality and safety.
Several FDA-approved medications contain bioidentical hormones. Estrace (estradiol as a pill or vaginal cream), Vivelle-Dot (an estradiol patch), Climara (another estradiol patch), EstroGel (estradiol gel), and Prometrium (micronized progesterone capsules) are all examples. These products go through the full FDA approval process, meaning their safety, effectiveness, dosing consistency, and purity have been tested and verified.
Compounded bioidentical hormones are custom-mixed by specialty pharmacies, often in the form of creams, troches, or pellets. These preparations are not reviewed or approved by the FDA for safety and efficacy. Compounding pharmacies are expected to follow quality standards set by the United States Pharmacopeial Convention (USP), which establishes benchmarks for identity, strength, quality, and purity. But a 2020 report from the National Academies of Sciences found it is “currently impossible” for clinicians to provide evidence-based guidance on the effectiveness or safety of each unique compounded formulation, because these individualized mixtures haven’t been studied in clinical trials.
The active hormone molecule is the same whether it comes from a pharmaceutical manufacturer or a compounding pharmacy. The difference lies in quality control, consistency of dosing, and the level of evidence behind each product. Compounded formulations carry risks of microbial contamination, incorrect dosing, and chemical impurities that FDA-approved versions are specifically tested to avoid.
Why “Natural” Can Be Misleading
Compounded bioidentical hormones are frequently marketed as a “natural” alternative to conventional hormone therapy. The plant origin of the raw material is real, but the final product is no less a pharmaceutical than any other prescription medication. Diosgenin goes through extensive chemical processing before it becomes estradiol or progesterone. The same plant-derived synthesis is used to make FDA-approved bioidentical products like Prometrium and the various estradiol patches and gels.
The word “natural” in marketing typically signals the plant source or the molecular match to human hormones, not that the product is unprocessed or free of laboratory intervention. Every bioidentical hormone, whether FDA-approved or compounded, is a manufactured pharmaceutical that happens to start its life as a compound in a yam or soybean root.