How do you decide whether to use a topical / transdermal form vs oral forms of hormone therapy?
For estrogen therapy — I prefer using estradiol which is the young woman’s predominant estrogen. Transdermal estrogen (patches and gels) are preferable because estradiol is absorbed directly into the bloodstream, bypassing the liver. When we take oral estrogen, it has to be processed through the liver before reaching the systemic circulation (this is known as the “hepatic first pass effect”). The liver breaks down 90% of the estrogen taken orally, so the dose of estrogen given orally need to be 10 times higher than the transdermal dose to reach comparable blood levels. Metabolism of this higher level of estrogen in the liver increases production of clotting proteins, thereby explaining the increase in blood clotting risk with oral estrogen use. Transdermal estrogen has been shown to NOT increase clotting risk, even in women with hereditary clotting disorder such as the Factor V Leiden mutation. Moreover, transdermal estradiol reaches the blood stream unaltered, so we know we are gettin
