I still believe that estrogen levels have the strongest impact on SHBG levels. When testosterone levels go up, estradiol follows, unless aromatase is adequately inhibited. This leads to elevated SHBG, which can then bind testost. Free testosterone is only a very small fraction of the total testost, the majority of which is bound to serum albumin, and secondarily to SHBG. So a relatively small increase in SHBG, triggered by estrogen, can markedly decrease the free, active test levels, with significant clinical effect.
Danazol is proven, although I wouldn't want to take it. It suppresses the whole axis, but if taken sparingly, will knock down the SHBG only.
Is not Proviron anti-e in action? If so, perhaps that is at least one of its purported actions on SHBG.
No more, I promise.