>>9525108Its a mix of testosterone/IGF1/DHT/other growth factor exposure in the womb and during puberty, plus blood flow. Some anecdotal evidence from bodybuilders that taking heavy regiments of HGH/other compounds increases girth a tiny bit (take that with a grain of salt), plus jelking people claiming they gain some size from that. Your best chance of gaining size as an adult is elongation surgery (at the loss of rigidity and function), implants (why...), as well as drugs which acutely increase blood flow to the area (viagra, testosterone, DHT, yohimbine, garlic, beetroot).
