Bioidentical progesterone is made from plant compounds, most commonly extracted from wild yams or soybeans. These plants contain a molecule called diosgenin, which serves as the raw starting material. Diosgenin can’t function as progesterone on its own, though. It must be chemically converted in a laboratory to produce a hormone that is structurally identical to the progesterone your body makes naturally.
The Plant Source: Diosgenin
The key ingredient behind bioidentical progesterone is diosgenin, a naturally occurring compound found in several plant families. The primary commercial source is the Dioscorea genus, a group of wild yams with roughly 137 species that contain diosgenin. Mexican wild yam (Dioscorea villosa) is among the most commonly used. Soybeans are another major source, and some manufacturers use fenugreek (Trigonella foenum-graecum) as well.
Diosgenin belongs to a class of plant chemicals called steroidal sapogenins. Its molecular structure happens to share a backbone with human steroid hormones, which is what makes it such a useful starting point. The pharmaceutical industry considers diosgenin a foundational precursor for producing not just progesterone but a range of steroid-based medications.
How Plants Become Hormones
The process of turning diosgenin into progesterone was pioneered in 1944 by chemist Russell Marker, who accomplished the first industrial conversion using Mexican yams at a lab in Mexico City. The technique he developed, now called the “Marker Degradation,” strips away most of the atoms in diosgenin’s side chain. What remains mirrors the side chain of progesterone. Further chemical modification of the steroid ring structure then yields progesterone itself.
This is a critical point: the conversion happens entirely in a laboratory. Your body does not have the enzymes needed to turn diosgenin into progesterone. Eating wild yams or applying raw wild yam extract to your skin will not raise your progesterone levels. The lab synthesis is what transforms an inactive plant compound into a hormone your body can recognize and use.
What “Bioidentical” Actually Means
The finished product has a molecular structure identical to the progesterone your ovaries produce. That’s what “bioidentical” refers to: not the plant origin, but the final chemical structure. Your body’s progesterone receptors can’t distinguish between this lab-made version and the hormone you produce naturally, because at the molecular level, they are the same thing.
This sets it apart from synthetic progestins, which are a different category of drugs. Synthetic progestins like medroxyprogesterone acetate (MPA) or levonorgestrel have altered chemical structures. They activate some of the same receptors as progesterone but can also interact with other hormone receptors, including testosterone receptors. These structural differences give synthetic progestins a different pharmacological profile, with different potency, different duration in the body, and potentially different side effects.
How It’s Delivered to the Body
Once synthesized, bioidentical progesterone is typically micronized, meaning it’s ground into extremely fine particles. This step dramatically improves absorption, because progesterone in its natural crystalline form is poorly absorbed through the gut. The micronized version, taken orally, produces blood levels comparable to what the ovaries generate during the second half of the menstrual cycle.
Absorption varies quite a bit from person to person. In one study of postmenopausal women given a single 300 mg oral dose, peak blood concentrations ranged from about 16 to 626 ng/ml. Older individuals tend to absorb more. This wide variability is one reason dosing often needs to be individualized. Bioidentical progesterone is also available in vaginal and topical formulations, which bypass the digestive system and deliver the hormone more directly.
The most widely known FDA-approved brand is Prometrium, sold as an oral micronized progesterone capsule. Compounding pharmacies also prepare custom formulations, though these are not subject to the same standardized manufacturing oversight as FDA-approved products.
Wild Yam Cream Is Not the Same Thing
This is one of the most common sources of confusion. Many over-the-counter creams are marketed as “wild yam progesterone cream” or “natural progesterone,” but most contain only unprocessed wild yam extract. That extract is rich in diosgenin, which sounds promising, but diosgenin has no proven hormonal activity in the human body. Without the laboratory conversion step, applying wild yam extract is not a meaningful way to supplement progesterone.
Some creams are specifically formulated to contain actual bioidentical progesterone that has already been converted from diosgenin in a lab. The difference matters enormously, and it’s not always obvious from the packaging. If a product lists only “wild yam extract” or “Dioscorea villosa extract” as an ingredient, it likely contains no active progesterone. If it lists “progesterone USP” or “micronized progesterone,” the conversion has already been done.