This general class of progesterone hormone, and it's synthetic varieties is about ubiquitous as any medication in current use for contraception and hormone therapy (for women with a uterus). If a compound acts like a progesterone its classified as a "progestin" and this class of medicines is very broad. In our bodies most of the progesterones are made by the ovary, it's made by the placenta, . used to prevent miscarriages, its been a treatment for PMS, it's been used to bring on missing periods, to prevent preterm birth, and it's used to protect the uterus from estrogen use in menopausal hormone therapy. Natural progesterones are usually the best for most of these therapies, but there are times when it is better not to use the bioidentical progesterone. So when we say there is a tug of war out there of information on which is better to be taking, natural or synthetic, we want you to understand there is a lot of scientific evidence and some of it conflicting. The natural progesterone is a compound that has only 21 carbons in the structure, it causes blood vessels to dilate, and it is anti-male hormone in most females. The 'synthetic' variety has 24 carbon molecules and constricts blood vessels and has been found to be slightly androgenic (producing male hormone effects). In truth all are synthetically manufactured, the natural, usually from yam sources, but the 'natural' progesterones are more similar to what is in our body. Like other hormones progesterone works by activating it's specific cell receptors. There are A and B progesterone receptors. of the progesterones stimulate the A progesterone receptors and some the B! So many varied effects of progesterone on tissues possible. As with other hormone therapies, the right medication, the right dosage, and the right monitoring make a big difference in the risks and benefits you will receive from these medications.
And what we hope to accomplish is a healthy understanding that all these progesterone treatments are very different, and confer very different risks to women depending upon the reason they are on the hormone, the dosage, the administration with other hormones and the duration of use. For birth control pills there is a great diversity in the types of progesterones in the pill, and many will have effects that act sometimes like the natural progesterone and sometimes like the synthetic. You cannot just make assumptions on this compound, there is still a lot for us to learn about. It is important to speak to your gyno, particularly if you are considering being on a progesterone of any type.