Something I’ve been seeing discussed more in the overlap b/w TRT communities and people running GLP-1s for recomp: estradiol becomes genuinely unpredictable when you stack the two, and I think the mechanism is straightforward once you work through it. Aromatase sits primarily in adipose tissue. As a GLP-1 drops body fat, you’d expect E2 to trend down over time. And it does, initially.
But if you’re running 500mg or more of testosterone simultaneously, you’ve got a much larger substrate load than ur shrinking fat tissue can aromatise predictably. Muscle aromatase picks up some of the slack, and the conversion pattern shifts in ways that don’t match whatever AI protocol worked during your previous blast at a higher starting body fat. This isn’t from a study. It’s a pattern that keeps coming up when people discuss recomp blasts alongside reta or sema. The practical takeaway seems to be: if you’re doing both, get bloods more frequently than feels necessary, and don’t anchor your AI dosing to past experience. The variables aren’t the same.