There's another problem that comes with low SHBG.
With low SHBG hepatic clearance of test is increased, because SHBG protect test from enzymatic degradation (mainly oxidative reactions). So you end up "pissing" test quicker. This can impair androgen/estrogen ratio since estrogen have a longer plasma half life than test. Moreover, not only androgen are bound by SHBG, but estrogens too.
So, for example. You inject test propionate and within hours plasma levels of testosterone increases. Then you take proviron, which binds avidly SHBG (it doesn't lower them, it binds them). Now you have a sudden spike of free test which is rapidly aromatized in estradiol and reduced to dht. Not only that, but the fraction of estradiol that was bound to SHBG now gets released, increasing free estradiol levels.
I just don't know why there are people who seems immune to these sides and people like me that are very sensitive.
Whenever i add 25 mg proviron on my test (and AI) regimen i get gyno symptoms and other estrogenic sides within hours.