One of the theories about the causes of PMS is that there is an imbalance between estrogen and progesterone. This theory has led to the treatment of PMS with progesterone. There have been over 20 scientific studies of the treatment of PMS with progesterone, the vast majority of which have found progesterone to be ineffective. There are a few small studies that have shown some relief of some symptoms of PMS with progesterone. These claims, made by some manufactures are unsubstantiated.
Yams produce a compound that is used by the pharmaceutical industry to produce progestogens.
The human body can NOT do this. Many PMS and menopausal remedies contain wild yam or Mexican yam extract. Often claims are made that this product is in fact progesterone, it is not. Dioscorea may have beneficial effects and it may be useful for some conditions, but it is not the same as progesterone. Use in pregnancy requires careful physician surveillance.