Very often, providers like to quote the Women's Health Initiative study as their guidelines. Even the FDA has warnings for Prometrium (bioidentical progesterone). I point out that the WHI study was a good thing and we learned much about Premarin (Conjugated HORSE estrogen) and synthetic progestins. The study was canceled due to too many instances of cancer in the study subjects.
I have read the study myself and there are problems with it. The purpose of the study was to determine if adding progestin to Premarin would improve the cardiovascular health of post-menopausal women. The problems with that study are:
1. Not a single participant was transgender.
2. Our prescribing protocol now includes bioidentical progesterone, not synthetic progestin. We are not prescribed CEE (Conjugated Equine Estrogen), i.e. Premarin.
3. You cannot look at the results of one drug and automatically assume that applies to all drugs in that category.
As part of that study, they looked at just Premarin and found it causes an increased risk of blood clots and stroke. They looked at just the progestins and found that it increases the risk of certain cancers. But they ignore the fact that neither of these products is found in the human body.
Yes, they are still prescribed. But as you pointed out, they do it at a low dose to avoid those risks. And some patients have a good outcome.
As yet, not one provider has been able to explain to me why we don't follow basic biology and do what the human body normally does. Estrogen levels rise at the beginning of the monthly cycle for the first half, then drop in the second half. Progesterone rises in the second half and drops at the end.
Estrogen provides fat distribution (bust, hips. and butt) and develops the ductwork inside the breast connecting to the nipple. This causes an increase in bust projection. Progesterone builds the glands (alveoli) that will produce milk later. This causes an increase in breast volume.
When pregnancy occurs, both estrogen and progesterone climb several times higher than baseline. This kicks breast development into high gear so that they will be fully matured and ready for lactation in nine months. Progesterone blocks prolactin so that lactation does not occur. Post-partum, (after birth), both hormones drop to baseline levels, allowing prolactin to cause milk ejection.
Because all of these hormones are bioidentical, because they come from the human body, the high levels do their job and do not cause all of the dangerous side-effects. If the risk is there, there would be very high numbers of pregnant women with cancer, blood clots, and stroke. But there isn't.
Sorry for the long post, but this is the long discussion I will have with my gynecologist. We will see what her response is.
