Lower Risk of Cardiovascular Events With Oral Estradiol Compared With Oral Conjugated Equine Estrogens
I’m not sure that many transwomen care one way or another where their estrogen comes from, but more and more science being done in the area of postmenopausal women is shining light on the sometimes important differences between what might otherwise be considered equivalent medications.
In this most recent study, Smith et al. (2014), two kinds of estrogen were studied: conjugated equine estrogen (CEE) [also known as estrogen sulfate, sold as Premarin] and oral estridiol [sold under a variety of names, including Estrofem and Vagifem]. Researchers tracked the health of 384 postmenopausal women over a six year period, during which ” the preferred formulary estrogen changed from CEEs to estradiol during the course of data collection.” Their focus was cardiovascular health — blood clots, heart attacks, and strokes, all commonly viewed as risk factors in HRT.
The results of the survey found that, while women in both groups saw increased risks compared to controls, the CEE group showed a statistically significant increase in risk for venous thrombosis (blood clots) and a non-statistically significant increase in risk for myocardial infarction (heart attack). Stroke risk appeared to be unchanged between the two groups.
Keep in mind that “statistically significant” and “realistically significant” are not the same thing. In practical terms, “statistically significant” could be something like an increase from a 1 in a million chance to a 2 in a million chance — statistically doubled, but still very unlikely. The conclusion to be drawn from this study is not to cease all use of CEEs immediately, but instead that “These findings need replication and suggest that various oral estrogen drugs may be associated with different levels of cardiovascular risk.” I.e. this is evidence of something that is worth further study.
If you are on Premarin, don’t stop taking your doses or run to your endocrinologist demanding a change of prescription. You’re not going to drop dead because of this study. Just be aware that, sometime in the future, doctors may change your source of estrogen to reduce your risk factors.