Good question, for which I'm not sure. I do know a couple of things though. Back in the early 90's it became legal for over the counter use (it previously required a prescription) and there was lots of hype on it being the second coming of steroids, the fountain of youth, yadda, yadda. And yes, it can cause a short burst of T production, all things being right for that to happen, however it doesn't last that long like the drug would, so it appears to have no real advantage for strength, size or whatever. Now remember, testosterone can be converted, to either estrogens or DHT's. DHT's are very bad for males, like acne, hair loss, prostate problems, etc etc. It sounds like I'm totally against this stuff, right? Nope, I talked it over with my physician due to my age (55) and he actually gave the go ahead with doseages in the 25-50 mg/day. I can tell you, it does not help in any way,shape or form with strength, gaining muscle, etc, but for us foggies, it does in fact give us a general overall better feeling of health, probably due to better sleep patterns, and other associated things. My advice would be for anyone under the age of 45 to not even consider any prohormone, as you probably have plenty circulating naturally, and it could upset the applecart so to speak, and it sounds as it may have with you.