[chrishoney]

The difference between taking something orally and sub-lingually or applying it cutaneously, is that anything that is taken orally goes through the digestive tract. Everything that is absorbed into the blood goes through the liver. All blood eventually is filtered by the liver,

Up to this point you are correct bigdave, everything in the circulatory system eventually is metabolized in the liver.

there is no direct connection between the digestive tract and the liver, except the bile duct, and things don't flow that way. Backwards that is.

Unfortunately, this is where you go seriously astray. Try a google search for the Hepatic Portal Vein System. This is part of the circulatory system that DIRECTLY connects the digestive system to the liver, before joining general circulation. Literally everything absorbed through the digestive tract passes directly to the liver via the hepatic portal vein system. This is the dreaded "first pass" through the liver. Older types of oral HRT (like Premarin) had something like 60 or 70% of the estrogen metabolized in the liver during the first pass, which is one reason dangerously high dosages were prescribed, especially for transgender women.

Transdermal or sublingual administration avoids the first pass (completely for transdermal routes and in my opinion only partially with sublingual administration.) Some part of sublingual and transdermally administered drugs will affect their target tissue BEFORE passing through the liver, but eventually, as with everything in general circulation, they WILL be metabolized by the liver.

Where have people gotten the idea that if you take something sub-lingually or apply it cutaneously, it doesn't go through the liver?

As with your error, it comes from an incomplete knowledge of anatomy and the physiology of digestion. Perhaps a little more study is in order before making such incorrect statements.

And yes, portions of PM DO need to be partially metabolized by the liver so that the overall estrogenic effect is potentiated by the initial steps of metabolization before it is ultimately cleared from the circulatory system.

Hope this helps.