As alcohol is toxic, your liver will break down the alcohol first. So estrogen won't be broken down when there is alcohol in your blood. This will result in an increased estrogen level, when this prolongs the elevated estrogen level will result in a decreased testosterone production.
Second, alcohol affects the leydig cells, Leydig cells are found in your whole body, but especially in your testicles. These cells produce testosterone, but not in the presence of alcohol.
Third, alcohol increases the amount of cortisone and prolactine. Increased levels of these hormones increases muscle breakdown and decreases the testosterone production.
You should stay away from alcohol as much as you can.