Over the last 100 years scientists have created thousands of "steroid" compounds to use in medicine. the vast majority of these compounds were never used in medicine and the research was filed away as data never to be used again. well, "supplement" companies have started using these old compounds in their "supplements" and they are considered steroids but because they have never been used in medicine, they are not banned in any way and the FDA has no idea what they are. since they have never been recognized as an illegal compound they are fair game to the supplement industry to use in their products since supplement companies are not forced to control what they put in their product. the FDA has no idea what compounds are in most of these "supplements" and until they have time to research the compounds the supplements are all over the place being sold as legal supplements when they are actually real steroids that were never placed on a banned substance list. once the FDA finds out what they are dealing with they ban that particular compound from the market. the thing is there are literally thousands of these unknown compounds that supplement companies are finding and using loopholes to use in their supplements. many "prohormones" were actually steroids made back in the 50's-60's that never made it into the medical field because other steroids were more effective and had less side effects. the majority of prohormones work very well but i would say they tend to have more sides than test or other medical AAS. all it takes is a bit of research and a good chemist to create these compounds and then you have a million dollar supplement to sell to anyone who wants to purchase it, by the time the FDA figures out what is going on they just change to another compound or a derivative of it and continue.
I know that the original M1T was very toxic and there were thousands of health issues because kids were abusing the hell out of it, but M1T was a very effective compound.
Most of the prohormones you see on the market today are fake and probably contain sugar and caffeine with no real hormone quality to them, that is why it is usually a good idea to stay away from todays prohormones, but the ones made in the past were in many cases real steroids that were never labeled and placed on a banned substance list.
My opinion is to use real human grade AAS or nothing at all.