SEriously though..
Actually studies show that most of the time our erections don't achieve their full potential, especially when you're older, out of shape, tired, hung over, or run-down in general.
I've never done test, but if it increases bloodflow (which it almost hast to if the hormone is increasing sex drive) then you will undoubtedly have larger erections, or atleast achieve your "peak" size more often.
An example is if you go for a second round of sex soon after the first. Generally you wont have as big or hard of an erection because the blood flow is reduced from lack of hormonal stimulus.