1. Low concentrations of nandrolone metabolites no longer permit a reliable conclusion as to the ingestion of nandrolone. In other words, it appears to be beyond scientific doubt that such low concentrations falling within what is often referred to as the “grey zone” (i.e., concentrations between 2,0 and 5,0 ng/ml), can as well be the result of endogenous production of the human body. When the concentration of nandrolone falls within the “grey zone”, the likelihood that nandrolone is produced endogenously, is decreasing exponentially within the limits of the “grey zone”.