The norandro products, instead of being similar to testosterone, are similar to nortestosterone. This steroid is anabolic in humans, but in men often has the unfortunate effect of producing partial or complete impotence, which is reversed on cessation of use. The body has enzymes to convert steroids from one form to other similar forms. Testosterone has three features which may be changed by enzymes. When any of them are changed, a different steroid results.
Enzymes often work two ways, though.
As it happens, if an enzyme can convert testosterone to another andro, say to androstenedione, then it can also convert that steroid back to testosterone. Let s start with androstenedione, often called simply androstene. Where testosterone has a hydroxyl group in a certain position, androstene has a keto group. All the rest of the steroid is exactly the same. So the body can convert testosterone to androstene back and forth by using the enzyme that can make this change.