@jlam1950

I did not interpret the info given as medical advice. I am grateful for any relevant shred of info so that can be a better advocate and question asker when I am seeing my doctors.

@jlam1950 yes loestrin was probably given this name to convey “low estrogen “
There are several forms of loestrin. Loestrin 1/20, loestrin 1.5/20 and loestrin 24 Fe.

Loestrin contains ethinyl estrodiol 10-30 mcg per pill depending on the type. 15 mcg of ethinyl estradiol is roughly equivalent to 1.5 mg of oral micronized estradiol in a young woman (as liver ages this equivalency changes). As an aside the average dose of oral estradiol for post menopausal women is 0.5-2 mg, This is a synthetic estrogen. it more potent (about 100 x more potent than natural estrogen), thus allowing a lower dose. They were manufactured for better absorption and stability, and are broken down less easily by the liver. This leads to differences in metabolism, receptor binding, and side effects. They have increased bioavailability which means more drug ends up in the bloodstream. Because they are broken down in the liver, as one ages and the liver’s ability to ‘detoxify’ or break down molecules decreases, the amount of synthetic estrodiol in the body increases.

Also, synthetic estrogens elevate hepatic (liver) protein synthesis more, leading to more blood clot, stroke and cholesterol risk, especially when taken orally. Btw, The lowest risk for clots, stroke (thrombotic) risk is with transdermal (skin patch) natural estrogen. Transdermal natural estradiol can be given at doses of 25- 100 mcg per day because it bypasses the first pass effect (the metabolism and inactivation of orally administered drugs, food too, in the GI tract, mostly liver, before they reach the general blood circulation, reducing bioavailability- meaning only a fraction of pill becomes active in the bloodstream) with direct bloodstream delivery. I probably could write this more succinctly. If questions, I am happy to try to better explain.

Synthetic estrogen was also has increased receptor activation which also makes them stronger than natural estrogen. They bind up to 2x better (affinity) than natural estradiol.