Does anyone know the medical reason why when a testicle is damaged and non-functioning, the testicle draws upward in the scrotum?

As mine atrophied and shrunk pulled up in the scrotum. The second one started to pull up almost into the pubic area before removal. The cord was pulling it up no weight pulling down anymore.

Interesting point this..

Bodybuilders on heavy dosage of Testosterone usually suffer fron their balls drawing upward.

They also suffer shrinkage caused by atrophy due to their lack of need to produce testosterone.

Could they be rising upward due to not weighing as much or is it a natural reflex?

It's simply a matter of weight. A healthy testicle weighs it down and the weight keeps it the scrotum. Atrophied testicles rise because they shrink due to death or lack of function. Body builders who use steroids cause their testicles to stop functioning, they stop producing testosterone and get smaller because of it. Sometimes body builders will then get shots of HCG to force their testicles to start producing testosterone again. Sometimes it works, sometimes not. When HCG works, their testicles are jump started into working and they "plump up" and fall back down into the scrotum.