Look up Progesterone. I believe Anadrol causes gyno through progesterone. I also remember reading somewhere that Anadrol itself can aggravate estrogen receptors. I think it was Llewellyn that said that but don't quote me on it.
Winny is said to have anti-prog properties and MANY that run the two together see no problems.
I'd personally run some sort of SERM with drol if one were gyno sensitive.
I've never touched the drug yet tho.