pretty sure my dick got bigger from testosterone since my erections were harder than they ever had been in my life and I believe this stretched the skin and developed the blood vessels in my little man. Gained like a half inch to the length.
I then became curious because I thought I was fucking with myself (i'd always heard you couldnt gain size after a certain age). I researched online, well found whole forums dedicated to stretching the penis....lots of it with blood volume work (squeezing lots of blood into the shaft). Lots of guys with testimonials about increase in size.
fwiw