proviron wont effect other steroids. but it is a steroid itself, so adding it in will boost you results, cause your adding in more steroid.
the free hormone hypothesis states that shbg (sex hormone binding gobulin) binds to free andorgens, and renders them unable to take action in the body. thus, accoring to the theory, only free adrogens are effective...and lower shbg is a good thing cause it results in more free test.
proviron reduces shbg, so people speculate its good for increasing free levels of other steroids.
however, ALL steroid reduce shbg, not just proviorn.
now with all that being said, the free hormone hypothesis is just that, a hpothesis, its very possible that another theory, "megalin induced expression of androgens" (or something like that).... oculd be true. this states that not only free, but also bouhnd andorgens can take action, through a rptoein called megalin that is present in shbg.
now, if the latter is true, that would mean not only is shbg not bad, but its actually good, because free hormones are metabolised and destroyed by the live very quickly...where as bound hormones are unable to be metabolised as quickly..mkenaing youll get more action from it.