The fact is that they both affect the exact same mechanism at the exact same step, and they all lower systemic estrogen levels. Even though studies, thus far, are showing no drop in HDL, you have to ask yourself how this could be so. Ultimately, it's the decreased systemic estrogen levels that reduce HDL, so anything that reduces estrogen, reduces HDL. I can't explain why the studies thus far haven't shown this, but it just doesn't make sense to me.