I was just meaning to correct what you wrote so readers who weren't aware of the brand name would be able to get the correct information. I always make typos and wouldn't mind others correcting me. In fact, I encourage it.
Prometrium can indeed have side-effects as it did for LShipley (thanks for sharing your story) but in general, at the doses typically prescribed for us, these side-effects appear (according to the literature) to be quite rare. Having a doctor supervise your treatment is, however, always recommended.
As far as estrogen goes, a higher incidence of gallstones in women does not necessarily mean estrogen is the culprit, it could be the fluctuating levels causing emotional and physical havoc, higher stress levels in women, genetics, their typical eating habits or dieting tendencies, the birth control pills they often take (that contain non bio-identical hormones), etc. There are so many confounding variables that cause and effect cannot be established.
Also, if an increased incidence of gallstones has been observed in women taking birth control pills, this does not necessarily mean that the same would occur in others taking bio-identical estradiol, a different molecule which much less adverse effects on the liver and overall metabolism. Progestogens are also contained in birth control pills so that the progestogen could be the culprit but it's also important to consider the differences between those progestogens and that which is naturally produced by women although, when taken orally, bio-identical progesterone seems to increase that risk, by a certain degree. The route of administration could be important as well due to less/more circulation in the liver, a different estrogenic profile (less or more estrone and by-products) so that before stating anything with certainty or making a generalized statement, it is best, I think, to consider all these factors. This is why I asked for more information, not because I wanted to poke at your ego. I'm just a very inquisitive person, try to get at facts as much as possible (understanding it's often impossible, alas!) and I sincerely apologize if anything I said bothered you, that was certainly not my intention.