The detection of the use of nandrolone and other 19-norsteroids is based primarily upon the identification of the main urinary metabolite, 19-norandrosterone (19-NA) in a concentration (derived from hydrolysis with β-glucuronidase) greater than the Decision Limit (DL), as established in the DL Technical Document. The presence of 19-NA in urine samples can be originated by: -the external administration of nandrolone or nandrolone precursor (as pharmaceutical or dietary formulation, progestogens, wild boar meat consumption); -the endogenous productions under particular physiological conditions (ovulation, pregnancy); -The ex-vivo production in urine by in-situ 19-demethylation of androsterone (A) (active urines)