I assumed I was supposed to take Estradiol swallowing it, as the Spiro. Then I started hearing about supposed advantages of taking E sublingual to avoid first pass liver metabolism. Here is a recent article on the subject:
https://transfemscience.org/articles/sublingual-e2-transfem/
The takeaway seems to be the problem that HRT traditionally is standardized for ciswomen and there is less predictability with individual results, in that trans people are undergoing HRT just as much for physical transformation as mood.
Another point for me is in context to those beginning therapy like myself, who may require preference over a steady level over time through the day rather than acheiving the highest level and then sharp decline over a few hours. After all, we are talking about many years of hormone therapy, and I can see health risks of fluctuating E levels early on. The author basically suggests take sublingually, but this also requires several tiny doses several times a day. Where non-compliance can be avoided, the practicality of a single dose 1x day is more reasonable.
Also my Endo said nothing regarding sublingual dosage, and I am also assuming this indication is reserved for patients who may be at risk. I mentioned alternative methods of administration, and she assured me it's all processed by the liver eventually either way.
I am also aware of the tendancy for young transwomen to prefer speed over possible health risks, and of course this is understood, as pushing dosages to maximum levels can be counterproductive, especially for us over 40.
I don't have any experience with oral or sublingual estrogen. Mainly that's because I'm prone to blood clots (genetic condition) and need to reduce my risk as much as possible. I inject estrogen subcutaneously instead. Injections and patches appear to have the lowest risk among the common delivery methods. Injections are also noted for their slower delivery of E. Peaks and troughs of E are minimized.