Progesterone is a natural hormone that our bodies make and cannot be found in Mirena. Mirena's hormones are synthetic. The theory is that Mirena's synthetic hormone fools our bodies into thinking it has created enough progesterone, so the body stops producing it and then becomes estrogen dominant. I don't think I'm the best at explaining it. Do a search for posts on here from Kabel. She hasn't posted in awhile, but she's done a ton of research on Mirena and how it causes estrogen dominance. You can also google it and find a lot of information that way. I copied and pasted from one of Kabel's previous posts below:
i am posting some links here for you to look into estrogen dominance, which i believe is probably affecting us all who have side effects to mirena. Many of us only had mirena not as contraception, but to help with existing conditions such as fibroids, endometriosis, thickened uterus etc and once we have the mirena removed, we are faced with our original condition, (which mostly seem to be caused by estrogen dominance!) as well as fighting the extra effects that mirena has caused.
For many, it also appears that at least some of the side effects can continue for many months after removal, and for SOME of us, the effects initially go away, only for a few of them to return 6 months later!! Why should this be? i believe it is due to our bodies being so messed up by mirena, that the hormone system just cannot get itself back on track after removal - it tries, which is why we initially feel better, but eventually it gives up, thus allowing our side effects back. Reading more about our natural hormone system and understanding that estrogen is prevalent in our western lifestyle will hopefully help us deal with not only side effects to mirena, but also help those of us who had pre existing conditions and even those people who have PMS, PCOS and worse.
It appears that using mirena or indeed, any chemical hormone treatment/contraception can throw our bodies into estrogen dominance and that many of us had estrogen dominance even before we starting using chemical hormones. If we are estrogen dominant, then surely Mirena which is "progesterone" based, is the way to go??? I am sure that is what our doctors thought too, but NO - because it is not progesterone, it is a chemical, which has a different molecular structure to our natural progesterone and does not work in exactly the same way as our natural hormone would. By taking up the hormone receptors in the body it may well be that the mirena chemical fools our bodies into thinking it already has enough progesterone and therefore we stop producing our own progesterone naturally. Once we get it removed, our bodies try hard to rebalance and for some of us, the hormone system cannot begin producing sufficient progesterone to keep us well and healthy.
I don't have all the answers and I am still learning about estrogen dominance but i wanted to share with you what I, Heater and others have found out so far. There are some conflicting bits of info in some of these websites - on some of the foods that we should either be eating or avoiding - unfermented soy is one in question - it is a phyto estrogen and takes up the estrogen receptors instead of the "bad" estrogen - this is better than having the bad estrogen there and can help some symptoms initially. However, i tend to agree with Dr. Lam (first link) that in the long term, it is still making us estrogen dominant, so should only be taken in small amounts and that instead of eating large quantities of phyto estrogens, we should be trying to strengthen our hormone systems by other means. Cibolina mentions adrenal problems in her post, below, and that appears to be a key ingredient of getting the hormones working again - cutting out caffeine for example is a must for anyone with any hormonal condition (like PMS, endometriosis etc) as well as anyone who has side effects from mirena. Also cleansing the liver is very important because it deals with excess estrogen as well as toxins possibly produced from the mirena. When the liver is not working 100% we are more likely to have hormone problems and side effects. Well, it is better for you to read about it all properly in the links below, then you can do more googling to find out more and make up your own mind! Dr. Lam's site has, i think the most complete information, but there are snippets in other sites too, so i will post a few here anyway, to start you off. Many sites say that progesterone cream(using a molecule extracted from wild yam that is identical to naturally found progesterone) is the answer - and for some, this may well be, but first, one should, if possible, get a saliva test to really check where all your hormones are at, then if you have too little progesterone and/or too much estrogen for the estrogen/progesterone ratio to be correct, start modifying your whole lifestyle in the way of what you eat and drink, the body creams and other xeno estrogen products that you use, and you may find that things gradually sort themselves out without having to use hormone cream. There are herbs and vitamins you can take to support the liver and the adrenal system too. Obviously if you can get to a naturapathic doctor who understands hormones or has heard of Dr. Lee, the original guy to talk about Estrogen dominance, then you are onto a winner!! Unfortunately many of us don't have access to someone like that, so have no choice but to try things out for ourselves. good luck and happy researching!