The use of natural or bioidentical hormones or synthetic hormones are very controversial. This months Townsend Letter had a great article on the Use of Progesterone. It explained the physiology, use and myths of the hormone progesterone.
The article demonstrated the following:
The most efficacious and safest way to protect the endometrium is with topical progesterone
Topical progesterone has been shown to effectively reduce estrogen’s mitogenic influence on the endometrium
Topical progesterone achieves higher cellular and blood levels of progesterone than oral progesterone
Progestins did not perform better than progesterone and carry far too much overall health risk to be considered for use in long term therapies
Progestins differ greatly from progesterone in form and function