Progesterone is a hormone made by men and women. It is a very specific molecule made in women primarily by the ovary and in men by the testes. But is also made by the adrenal gland, is even very likely made by hair follicles and by brain cells. There are receptors for progesterone essentially in every tissue of the body from nerves to brain cells to thyroid cells to muscle cells, fat cells and of course the breast, the ovary and the uterus. So you have to realize that when I say the word progesterone I am talking about that specific hormone. In fact when I decided after 12 years to share this information with my colleagues and with the class I was teaching I put it on the cover. That is progesterone, a specific molecular configuration. We make it in our body from cholesterol.

     The reason I emphasize that is the word estrogen does not mean that. Estrogen is a class name. There is no hormone named estrogen. There is estrone, estradiol, estrial. There is about 20-30 different estrogens. Horse estrogen is different from human estrogen and so on. But there is no hormone named estrogen. It is the name of a class like apple is the name of a class. There is no apple named apple, you have Delicious, Pippins, Granny Smith, you've got all these different apples they all have their own name. The same thing with estrogen.

     So this is one thing that bothers doctors. When you get a chance to talk to doctors they will think of progesterone in terms of a class name that there is a bunch of them, Provera and these artificial things are progesterone but they're not. And they'll think of estrogen as a unique thing and it is not, it is a class. They do different things. Estriol you make in large amount only during pregnancy, it doesn't do anything for hot flashes and probably doesn't do anything for maintaining minerals and bones. Estradiol is the only one that has a receptor in bone structure. So there is only one progesterone and all estrogens are not the same.