Two men ended up with advanced prostate cancer within six months of taking the same supplement drug advertised to boost stamina, increase muscle mass, and strengthen the heart.  

Both men in the report originally had low levels of prostate-specific antigen, a signal for prostate cancer "and then suddenly presented with widespread cancer within six months, which is unusual," Vickers said. "Clearly, these are very unusual cases, and there is appropriate concern with this agent."

The lethal combination is testosterone and estradiol and, though they are not disclosing what the supplement was, it is supposed to be pulled off the shelves. 

If you are considering a supplement, don't take it unless you are fully aware of all the side effects and implications of every single ingredient in it.