Through the medical university I attend, I got access to the journal of urology and found a recent study where platelet rich plasma injections to the penis increased its size, on average, by +0.3cm lengthwise and +0.5cm girthwise per injection. This gain was nearly linear for up to 5 injections for an average total gain of +1.5cm in length and +2.5cm.

I thought this was interesting.