Nandrolone (AKA 19-Nor-Testosterone or 19-Nor-Androstenolone) is an Anabolic Steroid. As the names suggests, it is related to Testosterone, a "male" hormone produced naturally in humans (male AND female) in varying quantities. All Anabolic steroids have "Androgenic" effects, which are the actions we commonly associate with Testosterone; masculinisation, aggression, virilisation, growth, but only up to a point, and with (serious!) reservations. Anabolic steroids also have "Anabolic" effects, those associated with growth of bone, muscle, red blood cells and mobilization of sugar.
These are more the effects sought by athletes abusing this range off drugs. Although some Testosterone type anabolics are orally active, they undergo a very heavy Liver process, removing a lot of their action, and also stressing the liver. Serious abusers, or legitimate patients tend to have injections, or to take safer more orally compatible anabolics like Stanazolol (the drug found twice in Ben Johnston's blood)
Anabolic steroids when used legitimately are used most often to stimulate some sort of growth, so are used in advanced osteoporosis, certain breast cancers, regeneration of red blood cells in kidney patients, puberty disorders, growth disorders, anemia, and to help gonad development (in males). Illegitimate use is focused on increasing muscle mass and strength, but will also increase red blood cell production, therefore blood thickness and oxygen-carrying capacity.
Nandrolone is produced in both males and females as a metabolite (by-product) of Testosterone, and studies have shown it can be elevated to a very detectable level. The studies however did NOT prove the elevated levels would exceed the IOC threshold for a positive test. They barely reached a quarter of this value.
The risks are something the takers ignore, or the suppliers say nothing about. Added to this is the fact that the IOC was able to find Nandrolone in over 14% of muscle-building supplements it tested, all claiming to be "natural", "safe" or "steroid free" athletes' health may be at risk simply by taking untested muscle or strength supplements.
The side effects are horrendous and are MORE likely to be serious the younger athletes take Anabolics. They include virilisation in males, early fusion of growing bones (stops growth) in teenagers, growth of breasts in males, androgenisation of females (loss of feminine sexual characteristics), Liver cancers, hepatitis, heart disease, cholesterol elevation, blood sugar elevation, epileptic fits, fluid retention, and ultimately heart-attack and stroke.
In defence athletes often ask why would anyone take Nandrolone when there are better illegal substances for middle-distance or endurance athletes? This is indeed debatable, and MAY suggest the taking has been more inadvertent, but maybe this last possibility is the exact reason they take it. They can suggest a defence saying it must have been in one of the supplements. Nandrolone helps muscle grow, and muscle stores glycogen, so no matter what the sport, if taken with the right type of training, it will improve endurance, strength and oxygen-carrying capacity.
Athletes should be VERY careful about what they take, and coaches more so. Remember health advice sites are rarely overtly commercial, but sites selling Ephedra, weight-loss and performance products are exactly that - commercial! You may receive a contaminated product in the post, but try chasing up the supplier! It's a case of - if the substance is found in your system then you are guilty regardless.