Bitch tits form when a male heavily abuses steroids. Given that all men have a small amount of oestrogen in addition to testosterone, steroids greatly increase the level of testosterone in a man's body.
However, in an attempt to keep testosterone and oestrogen at steady levels in relation to each other, the body produces much more oestorgen than necessary, resulting in feminine characteristics, namely breasts.
"No. He stopped taking them last year when they gave him bitch tits."