Synthetic hormones are manufactured to mimic the actions of your own hormones but the structure differs from your own hormones. This can lead to similar but not identical actions to your hormones and can also allow for an increased risk of side effects. Bioidentical hormones are made from a type of yam and are identical in molecular structure to your own hormones. This allows identical biological actions to your hormones and reduces the risks of side effects compared to synthetic hormones.