It is effective at lowering T in most people. Bica and others are generally considered when you have issues with spiro. Spiro is considered the 'lowest risk' because its used in so many contexts, like hormonal acne, and is very well understood and extremely cheap.

If you are doing injections, its pretty easy to just overwhelm your body with estrogen and do mono E therapy with no spiro. Some docs will probably still put you on spiro for 3ish months if you do injections, just because it makes the whole process smoother. If you find you have T issues on mono e, you can later add in progesterone for some extra T-blocking without blockers.

Its generally considered to be healthier to do injections and monotherapy, but if you have problems with needles/pain/scarring it might not be the best fit. On sublingual/patch medication its generally better to do it with spiro. Obviously, if your estrogen is good and your T is suppressed, dont worry, continue as normal!

Well it worked pretty well with me, and I even got breast buds on just spiro. But also my diabetic dad had the same experience (don't worry he started taking a different medicine lmao) so it was probably lucky genes. So many people are on it due to US regulations, not because it's good per se. Remember! Most of transgender healthcare is a side effect of cisgender healthcare. It often does not have trans people's best interests at heart.

If you are taking pills, anti-androgens are important. It's hard to get testosterone-suppressing estrogen levels without taking an unsafe amount of pills.

With injections, you can get your estrogen much higher without putting that load on your pill-processing guts.