Prohormones are natural hormones that in of themselves do not have much activity but rely on conversion by the body to the more active hormone for the desired effects.
They raise the levels of the male hormones testosterone and 19-nortestosterone. Prohormones contain metabolic precursors that your body transforms into the active hormones.
Prohormones are essentially one molecule short from being converted into those compounds. Certain enzymes in the human system supply the missing molecule. Androstenedione and Androstenediol convert to testosterone. Norandrostenedione and Norandrostenediol convert to nortestosterone.
The "andro" prohormones provide substrate for the formation of testosterone, while the "norandro" prohormones support the formation of nortestosterone.
Testosterone is the most important hormone in the male body for energy, libido, muscular size and strength. But many men are susceptible to the developing side effects from DHT and estrogen, which are metabolites of testosterone. Nortestosterone provides all of the anabolic effects of testosterone such as increased muscle size, strength, recovery from training and injury without the side effects because it does not convert to estrogen or DHT.