@gravity3

From my own experience, CTX levels reached their maximum suppression about 6–9 months after starting estrogen, similar to what’s reported, so you’ve almost certainly achieved that effect by now.

If you continue HRT, estrogen should, in theory, provide some protection against Prolia rebound. The challenge is that the degree of protection is not studied yet so you don’t know how much to rely on it.

Reclast option: a lower dose of Reclast hasn’t been studied for Prolia discontinuation, so that brings uncertainty also. When you add the “unknown” of estrogen’s contribution, it’s hard to say what reduced dose (if any) would be safe - and it depends on what your endo is comfortable with. Good that you only had 2 doses of prolia. Oral Fosamax could be another option if you could tolerate it, since it gives more flexibility in dosing and monitoring. Either way, monitoring CTX levels could be important.

Evenity option: the paper by Kendler looked at sequences involving Evenity (2yr) -> Prolia (1yr) -> Evenity (1yr), though not specifically for rebound prevention. For the year of Evenity after prolia, lumbar spine BMD increased 2.3% while hip and other sites were maintained. Again, with HRT in the mix, the effect could differ.

Each strategy could potentially work, though there is some uncertainty with each. I’m very interested in hearing your final choice and how it turns out. Thank you for exploring untested waters.