Bio-identical hormones is medical term for what are considered to be “natural,” versus synthetic, hormones. This means that bio-identical hormones are derived from plant sources, such as soy beans or yams.The phytoestrogens found in these plant sources are converted by enzymatic processes in a laboratory to the hormones identical to the ones produced by the body. Our bodies do not contain the enzymes required to convert the phytoestrogens to bio-identical hormones, so if one ingested the plant, there would be no effect because the body could not convert it to hormones.