Disposition of 17 beta-trenbolone in humans

The urinary excretion and metabolic pattern of 17 beta-trenbolone, a synthetic anabolic steroid hormone used as a growth promotor for beef cattle in several countries, has been studied in a human subject. For the separation of the metabolites of 17 beta-trenbolone, a reversed-phase high-performance liquid chromatographic method was established. The method was tested with metabolites obtained from incubation of 17 beta-trenbolone with rat liver microsomes. Fifteen metabolites could be well separated in one run by using a concave acetonitrile-water-methanol gradient. After ingestion of the tracer-labelled hormone at a dose of 0.04 mg/kg body weight 54% of the administered radioactivity was found in the urine after 26 h and 63% after 72 h. Of the urinary material 54% was present as glucuronides, which contained mostly 17 alpha-trenbolone, 17 beta-trenbolone and trendione. At least five other polar metabolites, presumably hydroxylated products, were found in smaller amounts, mostly in the unconjugated and sulphated fractions. Thus, the disposition of 17 beta-trenbolone in humans differs significantly from that in rats, which may have a bearing on the toxicological evaluation of the hormone.