I am on Estradiol and Spiro for HRT, but I was taking finasteride alone prior to this. Just to be safe: Everyone reacts to the medication differently, but this is my story.
I took finasteride alone to stop and possibly reverse the effects of balding, and it worked! We aren't allowed to talk about doses here, but to compare from what I have mostly read about, I was only taking 20% of the dose compared to most people including it in their HRT regime or for medical reasons (regarding their prostate).
When I began Estradiol, my physician asked me to stop the finasteride to see how the Estradiol alone may affect me. During that first month, the Estradiol and minoxidil did not do the trick for me, and a lot of my hair fell out revealing balding spots and thinning. In the follow up with my physician, we were going to discuss including finasteride again, but I asked if I could begin the Spiro. Now I am on Estradiol and Spiro, but I have been taking the minoxidil just in case, and some of the thin areas are noticeable if you look for it. I have been on HRT for about two months now.
I was wondering the same question as you, and I was either going to wait for the 8 month mark, or wait for the SRS/GRS. Why the 8 month mark? It's because of the many Youtube videos and posts I have seen, and I am thinking 8 months seems to be reasonably good threshold for many people -- I'm just eye-balling this number, so I have no scientific proof of it, but I'd be willing to test it for myself; if it doesn't work, I'll simply buy another cheap 3-mo supply of the foamy stuff off Amazon.
To Summarize:
- Finasteride alone worked.
- Estradiol alone didn't work.
- Estradiol and minoxidil helped, but not as good as Finasteride.
- Estradiol and Spiro, with minoxidil seems to be working; I haven't tried without minoxidil so I can't say if it helps.
- I'm waiting for the 8 month mark based on a non-scientific observation I have made.