Because it is nearly indetectable, HGH has become a substance of great concern in major league baseball and other sports battling allegations of rampant doping.
"Testosterone to me is so important for a sense of well-being when you get older," he says. "Everyone over 40 years old would be wise to investigate it because it increases the quality of your life. Mark my words. In 10 years it will be over the counter."
Stallone directed and co-wrote the new "Rambo" sequel, which arrived in theaters Wednesday.
