Transdermal HRT Safety and Efficacy

Safety Comparison

The American College of Cardiology recommends transdermal estradiol administration due to its significantly lower risk of venous thromboembolism compared to oral administration, with an odds ratio of 0.9 (95% CI, 0.4-2.1) for transdermal versus 4.2 (95% CI, 1.5-11.6) for oral estrogen preparations 2
Transdermal estradiol (as in Evorel Conti) has a neutral effect on Sex Hormone Binding Protein (SHBP), a marker for VTE risk, while oral estradiol (as in Kliofem) increases SHBP levels, according to the European Society of Cardiology 1
The first-pass liver metabolism with oral estrogen increases production of clotting factors, which is avoided with transdermal delivery, as stated by the American Heart Association 2

Blood pressure levels are statistically lower with transdermal estradiol-based HRT compared to oral formulations, likely due to more physiological impact on the renin-angiotensin-aldosterone axis, according to the American College of Cardiology 1
Oral HRT has been shown to offer no cardiovascular protection and may increase cardiovascular risk in some women, as reported by the European Society of Cardiology 3
Transdermal estradiol has less impact on lipid metabolism compared to oral formulations, as stated by the National Lipid Association 1

Transdermal 17β-estradiol (as in Evorel Conti) has been shown to reduce LDL levels and increase HDL, creating a more favorable lipid profile than oral formulations, according to the American College of Cardiology 1
Oral estradiol (as in Kliofem) has been associated with negative impacts on insulin tolerance compared to transdermal delivery, as reported by the European Association for the Study of Diabetes 1

For women with higher risk of thromboembolism, transdermal estradiol (Evorel Conti) is clearly the safer option, as stated by the American College of Cardiology 2, 1

Assuming all HRT formulations carry the same risk profile regardless of administration route - the transdermal route significantly reduces thromboembolism risk, as reported by the European Society of Cardiology 2, 1
Overlooking the importance of administration route when prescribing HRT to women with cardiovascular risk factors, according to the American Heart Association 3, 1
Failing to consider that the first-pass liver metabolism with oral estrogen increases production of clotting factors, which is avoided with transdermal delivery, as stated by the National Blood Clot Alliance 2