Yes mast can make you pee like a fountain day and night. It can skew your electrolyte balance (from the excess urination) and experience muscle cramps. Hair depends on the person, some guys from the moment they start they go balding fast and others are not affected at all. Unfortunately you have to try it yourself but in general it's probably the worst drug for hair.
Keep in mind, when you pee if you see that you can't aim where you previously aiming and your urine falls close to your tool, most probably your prostate starts to swell. DHT derivatives and mast specifically tend to worsen the prostate issues.
I didn't liked it at all as a drug, it's on the bottom of my list.