The type of HRT med AND how it is administered is what modifies the DVT risk.
On the whole, the more time a estrogen like substance has to go through
the liver to get inactivated, the more by-products, some promoting DVT,
are produced (not to mention the liver is working harder).
Ethinil estradiol is very very hard to metabolise by the liver thus very small doses are very potent.
Premarin is not as hard to metabolise, but still much harder than estrogen biologically identical
to what GG's have.
Since going through the liver is what produces the DVT by products, avoiding it reduces the risks
(but much less than switching from EE to estradiol).
The safest, is thus are in order
- Estradiol patch, same thing as GG's directly in the bloodstream then gets metabolised by liver
- Estradiol gels, gets to the bloodstream then gets metabolised by liver
- EV injections, added risk from injection itself. Cleaving valeric acid need a trip to the liver (cleaving doesn't produce any by-product, so benign). Once cleaved, same estradiol as GG. Tendency to produce varying E blood levels with high peaks which is why often its not given to older people.
- Sublingual estradiol
- Part is directly absorbed, other part goes through digestion (portal vein to liver, which produces a less potent by-product of estradiol, estriol).
- Sublingual estradiol valerate
- Oral Estradiol (goes through digestion), most estradiol degraded to less powerfull estriol before getting to destination
- Oral Estradiol Valerate (Same as Estradiol), though tends to produce less peaks since the EV -> E transformation slows down distribution in the body.
There's also EC injections (estradiol cypionate), which are probably about as safe as oral estradiol because the EC molecule is harder to process by the body than the EV molecule.
ethinil estradiol, conjugated estrogens and premarin are all riskier than any of these.
