Some of the names of prohormones which are available over the counter are: Androstenedione, Androstenediol, Norandrostenedione, and Norandrostenediol. There are six versions of these which are most prevalent:

4-androstene-3, 17 dione (4-Androstenedione)
5-androstene-3, 17 dione (5-Androstenedione)
4-androstene-3, 17 diol (4-Androstenediol)
5-androstene-3, 17 diol (5-Androstenediol)
19-nor4-androstene-3, 17 dione (19-Norandrostenedione)
19-nor5-androstene-3, 17 diol (19-Norandrostenediol)

Androstenedione is naturally produced in the adrenal glands, and is one step away from testesterone. In addition to being anabolic (muscle building), it is androgenic (increases male characteristics).

Norandrostenedione is one step away from nortestosterone (nandrolone). Nortestosterone is anabolic, but is less likely to increase male characteristics.

The difference between the dione and diol endings is small; dione means a ketone double bond, and diol means a hydroxyl double bond. What does this mean to you? Only that each requires different enzymes to convert to testosterone or nortestosterone.

Because each of the six androgens require different methods to be converted, many people stack them to maximize the anabolic effect. Even though there is a limit to the amount of each compound that can be converted, stacking allows for the maximum of each simultaneously.

Much has been made of the dangers of taking too much "andro". Scary predictions of liver damage, kidney failure, hair loss, prostate cancer, and more, have been made for those who use too much. Is andro safe?

Here are the facts about andro and norandro-

Hormone (testosterone or nortestosterone) levels peak within 90 minutes of ingesting andro/norandro, returning to normal within three hours. If you only take one dose of these products before an intense workout, the body will use the hormones produced during the workout.

There is little danger of excess hormones being converted. However, should you decide to take multiple doses in the same day, you should be aware of the possibility of conversion of any excess testosterone to estrogens or DHT.

Like any supplement, it is wise to take time off of andro/norandro occasionally. There is little chance that taking one bottle of a prohormone as directed above will have any negative effect upon your natural hormone production, but your body will become accustomed to the presence of these high amounts over time. Higher doses would be required to obtain the same anabolic effects. This would be undesirable, since higher doses increase the risk of conversion of excess testosterone.

People who should avoid andro/norandro; those under 18 years of age, or with advanced hair loss, or with prostate enlargement. Even individuals in these groups could probably safely use prohormones according to label directions, but might experience negative side effects at higher doses, more quickly than the general population. Better safe than sorry.