I'm 19 and have heard that i should not cycle till you are atleast in your late 20's, but if you only use testosterone is there really any big side effects? I just completed my personal trainer degree and at the end of the course we got to speak with some of the top personal trainers in my country, one of which had a master in human physiology & psychology (yes psychology, not that that really matters an awful lot). I asked him why don't old people get extra testosterone and he said that he had thought about the same thing and belive that old people should get extra testosterone. He was also in he's 50's and told me that he would go on testosterone when he retires and told me and the whole class that using testosterone for men is comparable in giving birth control pills to women. I never asked him about the use of testosterone in younger guys, but from what he said I find it hard to belive that using testosterone at my age is that dangerous when girls my age are using birth control pills.